Heterogeneous Charges Research Articles

Crystalline Covalent organic framework membrane with tailored chargeability for efficient pharmaceutical rejection by in-situ functionalization of polyethylene-imine

The nanofiltration (NF) membrane with better hydrophilicity, uniform pore size distribution, and dually charged properties is highly desirable to improve the pharmaceutical rejection, especially for the neutral and positively charged pharmaceuticals. Herein, a TpPa membrane was first in-situ crystallized via PTSA-mediated interfacial catalytic polymerization (ICP) strategy using 1,3,5-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa), followed by post-functionalization with PEI to narrow pore size, improve hydrophilicity, and tailor membrane charges to enhance pharmaceutical rejection. PTSA was used as a catalyst to enhance the crystallinity of the TpPa membrane. The PEI introduction narrowed the pore radius from 0.382 nm to 0.272 nm, improved surface hydrophilicity from 74.8°to 37.0°, and shifted surface charge from -19.25 mV to 11.15 mV. This PEI-functionalized TpPa (TpPa-PEI) layers exhibited heterogeneous charges on both sides with a positively charged top and negatively charged bottom. MgCl2 rejection increased from 13.67% to 83.0% without sacrificing water permeance. Additionally, pharmaceutical rejection and the water permeance of the optimal TpPa-PEI membrane exceeded those of the TpPaIP-PEI membrane fabricated without PTSA by about 3.3 and 1.3 times, respectively. Furthermore, compared to the pristine TpPa membranes, the substantially enhanced electropositivity of the optimal TpPa-PEI membrane led to 3-5 times increase in positively charged pharmaceutical rejection (94.1% for propranolol, 97.2% for sulpiride, and 71.2% for metformin). The synergy of negatively charged bottom TpPa-PEI layers and reduced pore size maintained sulfadiazine rejection of 62.1%. Mechanistic study confirmed that PEI penetrated 100 nm into the TpPa layer and cross-linked with the aldehyde groups, leading to tailored chargeability, improved hydrophilicity, and reduced pore size. Via a PEI cross-linking strategy, sub-nanometer channels of crystalline COF layers can be rationally designed, featuring precisely tailored chargeability and hydrophilicity, promising functionalization of the membrane pores and remarkably robust for water reuse.

Eco-FL: Enhancing Federated Learning sustainability in edge computing through energy-efficient client selection

In the realm of edge cloud computing (ECC), Federated Learning (FL) revolutionizes the decentralization of machine learning (ML) models by enabling their training across multiple devices. In this way, FL preserves privacy and minimizes the need for centralized data by processing data near the source. From a communication standpoint, only the model weights are exchanged between devices. By avoiding the need to send data to a centralized location for processing, FL reduces the energy required for data transfer and supports more efficient use of computing resources at the edge. FL is particularly advantageous for resource-constrained devices, such as smartphones and IoT devices. However, this limited computational power and battery capacity and the challenge of energy consumption are critical aspects of FL systems. This paper introduces Eco-FL, an innovative methodology designed to optimize energy consumption in FL systems, in the field of Green Edge Cloud Computing (GECC). Our approach employs a device selection process that considers the entropy of the data held by the devices and their available energy reserves. This ensures that devices with lower energy availability are less likely to participate in the training rounds, prioritizing those with higher energy capacities. To evaluate the efficacy of our methodology, we utilize FedEntropy, an entropy-based aggregation method, alongside established aggregation methods such as FedAvg and FedProx for performance comparison. The effectiveness of Eco-FL in reducing energy consumption without compromising the accuracy of the FL process is demonstrated through analyses conducted on three distinct datasets. These analyses vary the β parameter of the Dirichlet distribution and account for scenarios with both homogeneous and heterogeneous initial device charges. Our findings validate Eco-FL’s potential to enhance the sustainability of FL systems by judiciously managing client participation based on energy criteria, presenting a significant step forward in the development of energy-efficient FL.

Mixed colors by combustion of mixed homogeneous pyrotechnics and heterogeneous charges

AbstractThe combustion of mixed homogeneous pyrotechnic compositions and heterogeneous charges is studied experimentally with the aim of producing a selectable wavelength signal flare. The heterogeneous charge was perceived as a mixed color by a distant observer. A model for color chromaticity coordinates of homogeneous mixtures was derived that includes the mass, mass‐based burn rate and luminous intensity ratios of the constituting color compositions. This model can predict the expected dominant wavelength of a mixed composition. It can also handle the spacing of chromaticity coordinates of mixed compositions on a straight line in the CIE diagram between chromaticity coordinates of constituting colors. With two series of color composition mixtures, it was demonstrated that the chromaticity coordinates of the mixtures could be at, or slightly deviate, from the straight line connecting the chromaticity coordinates of the constituting compositions. It indicates there is little to no influence of flame temperature and mutual pyrotechnic reactions.

The effect of heterogeneous surface charges on mixing in a combined electroosmotic/pressure-driven micromixer

The effect of heterogeneous surface charges on mixing in a combined electroosmotic/pressure-driven micromixer

Electrostatic model of dielectric elastomer generator based on finite element

When dielectric elastomer materials are used for power generation, bias voltage is applied at both ends of dielectric elastomer film, and there are equal amounts of heterogeneous charges on both sides of the film, so Maxwell electrostatic force is always coupled in the process of power generation. In order to investigate the distribution of Maxwell stress in dielectric elastomer material under electric field, the electrostatic model of dielectric elastomer generator is established in COMSOL finite element simulation software environment in this paper. The distribution of electrostatic force is studied from two aspects of theoretical derivation and simulation, and the magnitude and direction of electrostatic force are determined. The simulation results show that the Maxwell electrostatic force can be equivalent to the tensile force along the film plane and the extrusion force perpendicular to the plane, and they are the same.

Partition and selectivity of electrolytes in cylindrical nanopores with heterogeneous surface charge

In this work, ion partitioning and selectivity in cylindrical nanopores with heterogeneous surface charges at equilibrium with reservoirs are investigated by a two-dimensional (2D) classical density functional theory (DFT). We present an efficient numerical method for the large 2D system in which the fast Hankel transform and fast Fourier transform are used to calculate convolution integrals, and a hybrid method of Picard iteration and Anderson mixing is used to solve the Euler-Lagrange equations. The performance of the 2D DFT is tested by calculating the profiles of a model electrolyte in long homogeneous cylindrical nanopores. The profiles from the 2D DFT model matches well with those from a 1D DFT, and the computing time of the hybrid iteration algorithm is six times shorter than that of pure Picard iteration. We apply the model to electrolytes in cylindrical nanopores with heterogeneous surface charges. It is found that the ion adsorption and selectivity are strongly affected by the surface charge pattern, the magnitude of the surface charge, the size of charged domains on the surface, and the pore size.

Structural Formation of the Cement Pastes Based on the Concrete Modified Dispersed Mineral Components

With the increase in the number of finely dispersed mineral additives in concrete, their water demand increases and the effect of micro-filling weakens. To solve this problem, various methods of dry surface modification are proposed. As a result of the finely dispersed mineral powders’ surface modification, an improvement in their rheological characteristics, a decrease in wettability, a change in granulometry and other properties are achieved. This article discusses the surface modification effect’s laws in a high-voltage electric field on the autogenous properties of mineral dispersed concrete components, structure formation processes, mechanical properties, and cement stone hydration products. According to the results of the study, it was found that the surface modification of bulk materials - concrete components - in a high-voltage electric field changes autohesion properties in comparison with control samples. The data indicate lower values ​​of bulk density and angle of repose. This is due to a change in the balance of forces that arise during the mutual contact of particles after surface modification. With a certain balance of these forces, autohesion will contribute to the dense packing of particles and thereby affect the structure formation processes. The results of changes in the plastic strength of cement pastes confirm that there is an intensification of the structure formation process. Moreover, a more intense increase in plastic strength is observed during bipolar charging of particles in comparison with unipolar charging. This is due to an increase in the number of heterogeneous charges in the system and, as a consequence, an increase in the strength of adhesive contacts, as evidenced by the data of X-ray phase analysis.

Electrostatic self-assembly synthesis of ZnFe2O4 quantum dots (ZnFe2O4@C) and electromagnetic microwave absorption

Making effective usage of quantum size effect is a foregrounded strategy to design and fabricate excellent electromagnetic microwave absorption materials. In this research, ZnFe2O4 quantum dots were coated by hybrid amorphous carbon to form a sea islands structure by a facile electrostatic self-assembly synthetic technology. Simultaneously, the rejection of heterogeneous charges leads to the formation of quantum dots, by which the quantum size effects on dielectric and magnetic characteristic were investigated. Consequently, multiple hetero-interface and interfacial polarization was originated from polycrystalline feature of ZnFe2O4 with spinel and inverse spinel structures. In particular, the electromagnetic microwave absorption properties of ZnFe2O4 were greatly optimized, as the minimized reflection loss reached −40.68 dB at the frequency 11.44 GHz and thickness 2.5 mm, while the effective bandwidth corresponding was 3.66 GHz (from 9.87 to 13.52 GHz). The largest effective bandwidth was 4.16 GHz (from 8.08 to 12.24 GHz) with a thickness of 3 mm. It is suggested that high performance of microwave absorption of ZnFe2O4 quantum dots was well guided by the optimized impedance matching and attenuation constants.

Analytical Solution of Time-Periodic Electroosmotic Flow through Cylindrical Microchannel with Non-Uniform Surface Potential.

Time-periodic electroosmotic flow (EOF) with heterogeneous surface charges on channel walls can potentially be used to mix species or reagent molecules in microfluidic devices. Although significant research efforts have been placed to understand different aspects of EOF, its role in the mixing process is still poorly understood, especially for non-homogeneous surface charge cases. In this work, dynamic aspects of EOF in a cylindrical capillary are analyzed for heterogeneous surface charges. Closed form analytical solutions for time-periodic EOF are obtained by solving the Navier–Stokes equation. An analytical expression of induced pressure is also obtained from the velocity field solution. The results show that several vortices can be formed inside the microchannel with sinusoidal surface charge distribution. These vortices change their pattern and direction as the electric field change its strength and direction with time. In addition, the structure and strength of the vorticity depend on the frequency of the external electric field and the size of the channel. As the electric field frequency or channel diameter increases, vortices are shifted towards the channel surface and the perturbed flow region becomes smaller, which is not desired for effective mixing. Moreover, the number of vorticities depends on the periodicity of the surface charge.

Vertical interphase enabled tunable microwave dielectric response in carbon nanocomposites

Interface constitutes a significant volume fraction in nanocomposites, and it requires the ability to tune and tailor interfaces to tap the full potential of nanocomposites. However, the development and optimization of nanocomposites is currently restricted by the limited exploration and utilization of interfaces at different length scales. In this research, we have designed and introduced a relatively large-scale vertical interphase into carbon nanocomposites, in which the dielectric response and dispersion features in microwave frequency range are successfully adjusted. A remarkable relaxation process has been observed in vertical-interphase nanocomposites, showing sensitivity to both filler loading and the discrepancy in polarization ability across the interphase. Together with our analyses on dielectric spectra and the relaxation process, it is suggested that the intrinsic effect of vertical interphase lies in its ability to constrain and localize heterogeneous charges under external fields. Following this logic, systematic research is presented in this article affording to realize tunable frequency-dependent dielectric functionality by means of vertical interphase engineering. Overall, this study provides a novel method to utilize interfacial effects rationally. The research approach demonstrated here has great potential in developing microwave dielectric nanocomposites and devices with targeted or unique performance such as tunable broadband absorbers.

The self-assembly and patterning of thin polymer films on pyroelectric substrates driven by electrohydrodynamic instability

We use hot PDMS to parallelly transfer and print heat energy onto lithium niobate substrates to induce a local pyroelectric effect. The heterogeneous electrostatic charges built from hot μCP can guide the self-assembly of different thin polymer films and develop them into micropattern.

Unified Hamiltonian for conducting polymers

Two transferable physical parameters are incorporated into the Su–Schrieffer–Heeger Hamiltonian to model conducting polymers beyond polyacetylene: the parameter γ scales the electron–phonon coupling strength in aromatic rings and the other parameter ε specifies the heterogeneous core charges. This generic Hamiltonian predicts the fundamental band gaps of polythiophene, polypyrrole, polyfuran, poly-(p-phenylene), poly-(p-phenylene vinylene), and polyacenes, and their oligomers of all lengths, with an accuracy exceeding time-dependent density functional theory. Its computational costs for moderate-length polymer chains are more than eight orders of magnitude lower than first-principles approaches.

Rectification of Nanopores at Surfaces

At the nanoscale, methods to measure surface charge can prove challenging. Herein we describe a general method to report surface charge through the measurement of ion current rectification of a nanopipette brought in close proximity to a charged substrate. This method is able to discriminate between charged cationic and anionic substrates when the nanopipette is brought within distances from ten to hundreds of nanometers from the surface. Further studies of the pH dependence on the observed rectification support a surface-induced mechanism and demonstrate the ability to further discriminate between cationic and nominally uncharged surfaces. This method could find application in measurement and mapping of heterogeneous surface charges and is particularly attractive for future biological measurements, where noninvasive, noncontact probing of surface charge will prove valuable.

Characterization of the Mixing Layer Resulting from the Detonation of Heterogeneous Explosive Charges

A dense, two-phase numerical methodology is used to study the mixing layer developing behind the detonation of a heterogeneous explosive charge, i.e., a charge comprising of a high explosive with metal particles. The filtered Navier–Stokes equations are solved in addition to a sub-grid kinetic energy equation, along with a recently developed Eulerian–Lagrangian formulation to handle dense flow-fields. The mixing layer resulting from the post-detonation phase of the explosion of a nitromethane charge consisting of inert steel particles is of interest in this study. Significant mixing and turbulence effects are observed in the mixing layer, and the rms of the radial velocity component is found to be about 25% higher than that of the azimuthal and zenith velocity components due to the flow being primarily radial. The mean concentration profiles are self-similar in shape at different times, based on a scaling procedure used in the past for a homogeneous explosive charge. The peak rms of concentration profiles are 23–30% in intensity and decrease in magnitude with time. The behavior of concentration gradients in the mixing layer is investigated, and stretching along the radial direction is observed to decrease the concentration gradients along the azimuth and zenith directions faster than the radial direction. The mixing and turbulence effects in the mixing layer subsequent to the detonation of the heterogeneous explosive charge are superior to that of a homogeneous explosive charge containing the same amount of the high explosive, exemplifying the role played by the particles in perturbing the flow-field. The non-linear growth of the mixing layer width starts early for the heterogeneous explosive charge, and the rate is reduced during the implosion phase in comparison with the homogeneous charge. The turbulence intensities in the mixing layer for the heterogeneous explosive charge are found to be nearly independent of the particle size for two different sizes considered in the initial charge. Overall, this study has provided some useful insights on the mixing layer characteristics subsequent to the detonation of heterogeneous explosives, and has also demonstrated the efficacy of the dense, multiphase formulation for such applications.

Simulation of impulse effects from explosive charges containing metal particles

The propagation of an explosive blast wave containing inert metal particles is investigated numerically using a robust two-phase methodology with appropriate models to account for real gas behavior, inter-phase interactions, and inter-particle collisions to study the problem of interest. A new two-phase Eulerian–Lagrangian formulation is proposed that can handle the dense nature of the flow-field. The velocity and momentum profiles of the gas and particle phases are analyzed and used to elucidate the inter-phase momentum transfer, and its effect on the impulsive aspects of heterogeneous explosive charges. The particles are found to pick up significant amounts of momentum and kinetic energy from the gas, and by virtue of their inertia, are observed to sustain it for a longer time. The impulse characteristics of heterogeneous explosives are compared with a homogeneous explosive containing the same amount of high explosive, and it is observed that the addition of solid particles augments the impulsive loading significantly in the near-field, and to a smaller extent in the far-field. The total impulsive loading is found to be insensitive to the particle size added to the explosive charge above a certain cut-off radius, but the individual impulse components are found to be sensitive, and particles smaller than this cut-off size deliver about 8% higher total impulse than the larger ones. Overall, this study provides crucial insights to understand the impulsive loading characteristics of heterogeneous explosives.

Discoveries in Detonation of Molecular Condensed Explosives in the 20th Century

A number of experimental results that could not be satisfactorily explained within the framework of the Grib—Zel'dovich—Neumann—Doring detonation theory are reviewed, namely, the oscillating detonation of some liquid high explosives (HE), the weak dependence of the time of detonation transformation of heterogeneous charges on their structure (particle size, liquid or solid state, etc.) with a strong dependence of the critical diameter of detonation on the structure, and the extremely weak dependence of the detonation rate of liquid HE on the charge diameter with a significant value of the critical diameter of detonation. These studies yielded the following results: 1) for each heterogeneous HE, a typical shock–wave pressure p* and a typical initial density ρ0* were found, such that, for their low values, HE transformation follows the mechanism of hot points (depends on the charge structure), and for high values of these parameters, HE transformation obeys the homogeneous mechanism (does not depend on the charge structure); 2) two new theoretical notions were discovered and used in the detonation theory: the phenomenon of breakdown of the chemical reaction in the shock–wave front by rarefaction waves and the notion of a “shock jump,” which reflects the specific character of action of shock waves on complex multiatomic molecules of condensed HE. It was also shown that the discovery of the parameters p* and ρ0* and the breakdown and “shock jump” phenomena allowed one to confirm experimentally the explanations of the above observations, which are incompatible with the Grib—Zel'dovich—Neumann—Doring detonation theory, to propose the structure of the front of detonation waves both in homogeneous (stable and oscillating) and heterogeneous HE whose basic property is HE transformation (partial or complete depending on the HE power and initial density) already in the shock–wave front, and to proposed principally new ideas on the nature of the critical diameter of detonation of homogeneous and heterogeneous HE.

Numerical modeling of the effect of temperature and particle size on shock initiation properties of HMX and TATB

Abstract The three-dimensional Eulerian reactive hydrodynamic code 3DE has been used to investigate the effects of particle size (and the remaining void or hole size) and of initial temperature on the shock initiation of heterogeneous explosive charges of HMX and TATB. Shocks interacting with HMX and TATB containing various hole sizes have been modeled. The void fraction was held at 0.5% while the spherical hole sizes were varied from 5.0- to 0.00005 mm radius. The shock pressure was also varied. As the hole size in TATB was varied from 5.0 to 0.5 mm, the explosive became more sensitive to shock. Decreasing the hole size to 0.0005 mm resulted in failure of the shock wave to build toward a propagating detonation. This is similar to the results previously reported for TNT. HMX became more sensitive to shock as the hole size was varied from 0.5 to 0.005 mm. The hole size had to be decreased to 0.0005 mm before the explosive became less shock sensitive. Smaller hole sizes (0.00005 mm) resulted in failure of t...

Spin wave and attenuation of liquid explosive detonation

The detonation of nitromethane and a dinitrotoluene solution in bistrinitroxyethylnitramine when the diameter of the cylindrical charge is close to the critical was investigated with the aid of high-speed photography of the luminosity of the lateral and end cylinder surfaces and the recording of the spin wave surface using sampling plates with an air gap. It was discovered that the appearance of penetrating spinning absence-of-reaction waves, which are responsible for the attenuation of liquid explosive detonation, is closely related to the spread of detonation spin waves over the charge surface (or immediately below it). The spin waves, which are instrumental in the propagation of a normal detonation in weakly heterogeneous cast charges consisting of trotyl-hexogene and trotyl-PETN, in the case of liquid explosives probably inhibit the detonation process by inducing the formation of penetrating absence-of-reaction spin waves. It is shown that the spin wave velocity corresponds to the degree of material compression in the near-surface layer, as calculated according to the Dremin-Trofimov model (it can be only slightly above it.)

Isoelectric focusing of monoamine oxidase subtypes as identified by MAO inhibitors

Monoamine oxidase from various human tissues from several individuals was labeled with [ 3H]pargyline and solubilized by means of Triton X-100 or Triton X-100 and urea. The specificity of the labeling was assessed using various selective, reversible and irreversible inhibitors as pharmacologic tools in competition experiments. The labeled material was submitted to isoelectric focusing on polyacrylamide gels according to one- and two-dimensional electrophoretic procedures and with fluorographic detection. While the differences in electrophoretic mobility of the two subtypes, MAO-A and MAO-B, could be replicated the subtypes showed identical although heterogeneous charges in isoelectric focusing. This contrasts with recent findings of clear differences in the primary structure of monoamine oxidase subtypes and thus needs further clarification.

The detonation parameters of TG 68/32 heterogeneous charges

1. In this work the parameters for the detonation wave front in cast explosives, density 1.672 g/cm3, containing 68% trotyl with the addition of 32% of very dense particles of hexogene of different dimension, have been measured. 2. With an increase in the particle dimensions the detonation velocity of the charges investigated increases, but the pressure at the wave front falls in comparison with the corresponding parameters in charges containing finely dispersed hexogene. 3. The explanation of this phenomenon lies in the fact that in heterogeneous charges an insufficiently compressed region of detonation occurs