Bare Charge Research Articles

On a Connection of the Fine Structure Constant with Zero-Point Fluctuations of the Electromagnetic Field in Vacuum*

Duality of four-dimensional electrodynamics and two-dimensional field theory leads to a finite value $$ {e}_0=\pm \sqrt{\hbar c} $$ of the point-like bare charge with the fine structure constant a 0 = 1/4π. On the other hand, the calculated (by several authors) energy shifts E B = a B ћc/2r and E L = a L ћc/a of zero-point electromagnetic vacuum fluctuations by neutral conducting shells of a sphere of radius r and a cube of edge a are defined by the dimensionless parameters αB and αL, which differ from each other by less than 0.8% and even more weakly differ from the fine structure constant α times 4π, since a L < 4πa < a B. According to the duality, 4πα = α/α0 and α0αL < α < α0αB, the values αB and αL can be considered approximate reciprocals of the vacuum dielectric permittivity. Since the difference of α0αL from α appears to be less than 0.05%, we discuss here the possibility of circumscribing the sphere polyhedrons γ, the conducting shells of which could shift the zero-point energy by the amount Eγ = αγ_c/2r, where the parameter αγ is more close to 4πα than αL for the cube. We focus on the relativistic and adiabatic invariances of the parameters αγ.

MeasuringaμHLOwith space-like data

After reviewing the traditional way of computing the leading order hadronic correction to the muon (g-2) through a dispersive approach via time-like data, I will present a novel approach, based on the measure- ment of the effective electromagnetic coupling in the space-like region extracted from Bhabha scattering data. We argue that this new method may become feasible at flavor factories, resulting in an alternative determina- tion potentially competitive with the accuracy of the present results obtained with the dispersive approach via time-like data 1 αem running and the Vacuum Polarization Precision physics requires appropriate inclusion of higher order effects and the knowledge of very precise parameters of the electroweak Standard Model SM. One of the basic input parameters is the fine structure constant which de- pends logarithmically on the energy scale (1). At zero mo- mentum transfer, the QED coupling constant α(0) is very accurately known from the measurement of the anoma- lous magnetic moment of the electron and from solid-state physics measurements: α −1 (0) = 137.03599976(50). (1) Vacuum polarization effects lead to a partial screen- ing of the charge in the low energy limit (Thomson limit) while at higher energies the strength of the electromag- netic interaction grows. This is due to virtual lepton and quark loop corrections to the photon propagator. This effect can also be understood as an increasing pen- etration of the polarized cloud of virtual particles which screen the bare electric charge of a particle. Thus, at large distances, we observe a reduced bare charge due to this effect of screening. As we probe closer we penetrate into the cloud of virtual particles, decreasing the screening effect and observing more of the bare charge and thus a strengthening of the coupling The charge has to be replaced by a running charge:

Communication: Charge, diffusion, and mobility of proteins through nanopores.

Implementation of Einstein's law connecting charge, diffusion coefficient, and mobility to interpret experimental data on proteins from single molecule electrophoresis through nanopores faces serious difficulties. The protein charge and diffusion coefficient, inferred with the Einstein law, can be orders of magnitude smaller than their bare values depending on the electrolyte concentration, pore diameter, chemical nature of the pore wall, and the externally applied voltage. The main contributors to the discrepancies are the coupled dynamics of the protein and its counterion cloud, confinement effects inside the pore, and the protein-pore-surface interaction. We have addressed these ingredients by harking on classical theories of electrophoresis of macroions and hydrodynamics inside pores, and deriving new results for pore-protein interactions. Putting together various components, we present approximate analytical formulas for the effective charge, diffusion coefficient, and mobility of a protein in the context of single molecule electrophoresis experiments. For the omnipresent pore-protein interactions, nonlinear dependence of the velocity of protein on voltage sets in readily and analytical formulas for this effect are presented. The derived formulas enable the determination of the bare charge and size of a protein from the experimentally measured apparent values.

Mayer function perturbation theory of effective interaction of charged colloids

In this paper, the effective interaction between charged colloids has been studied based on the standard Mayer function perturbation theory. With the formalism developed in this paper, the effective interaction as a function of Mayer functions and the correlation functions of the homogeneous microions is obtained. The asymptotic behaviour of the effective interaction at large distance is analysed in detail. It is found that at large distance the effective interaction is Yukawa like, provided the bare charge is replaced by the renormalised one. Exact expressions for the renormalised charge and the decay length as functions of the short-range part of the Mayer function and that of the correlation function of the homogeneous microions are obtained. With perturbation methods, it is easy to see how the effective interaction at large distance is affected by microion correlations and nonlinearity.

Analysis and Simulations of Lensless Imaging with Intensity Correlation Method

Traditional imaging method use high precision mirrors to focus the lightfield toobtain object’s imaging, this method is affected by aberrations and atmosphere turbulence. However lensless imaging method can get high resolution without using lens and mirrors ,it will make the system compact light weight. In this paper,we analysis and simulated a new lensless imaging method with intensity correlation, by this way,we can get high resolution imaging by bare Charge Coupled Device (CCD) only,and the simulations show that this method can obtain good image to low angular diameter object.

Small-scale chamber test for internal blast performance

The viability of using gram-scale amounts of explosives in a small test chamber to assess internal blast performance and predict effects at larger scales is investigated. Peak quasi-static pressures from five explosive formulations were measured, and energy released per gram was calculated. The smaller test used 12-g charges loaded in a steel holder, while data selected from the larger test was from bare charges between 2.7 and 21 kg. The energies for a given explosive were comparable for each size charge tested in the larger chamber. In the smaller chamber the energies were less, most likely due to heat losses to the holder. Explosives with the highest concentration of explosive ingredients incurred the highest energy losses in the small chamber. The current design of the smaller test provides a reasonable ranking of explosives with similar concentrations of explosive ingredients, thereby validating the use of the test for the newer explosives being assessed. However, it may be possible to obtain consistent rankings for all explosives given a change to the holder design in the smaller test.

Coupling between bulk- and surface chemistry in suspensions of charged colloids

The ionic composition and pair correlations in fluid phases of realistically salt-free charged colloidal sphere suspensions are calculated in the primitive model. We obtain the number densities of all ionic species in suspension, including low-molecular weight microions, and colloidal macroions with acidic surface groups, from a self-consistent solution of a coupled physicochemical set of nonlinear algebraic equations and non-mean-field liquid integral equations. Here, we study suspensions of colloidal spheres with sulfonate or silanol surface groups, suspended in demineralized water that is saturated with carbon dioxide under standard atmosphere. The only input required for our theoretical scheme are the acidic dissociation constants pKa, and effective sphere diameters of all involved ions. Our method allows for an ab initio calculation of colloidal bare and effective charges, at high numerical efficiency.

Counterion condensation on spheres in the salt-free limit

A highly-charged spherical colloid in a salt-free environment exerts such a powerful attraction on its counterions that a certain fraction condenses onto the surface of a particle. The degree of condensation depends on the curvature of the surface. So, for instance, condensation is triggered on a highly-charged sphere only if the radius exceeds a certain critical radius R*. R* is expected to be a simple function of the volume fraction of particles. To test these predictions, we prepare spherical particles which contain a covalently-bound ionic liquid, which is engineered to dissociate efficiently in a low-dielectric medium. By varying the proportion of ionic liquid to monomer we synthesise nonpolar dispersions of highly-charged spheres which contain essentially no free co-ions. The only ions in the system are counterions generated by the dissociation of surface-bound groups. We study the electrophoretic mobility of this salt-free system as a function of the colloid volume fraction, the particle radius, and the bare charge density and find evidence for extensive counterion condensation. At low electric fields, we observe excellent agreement with Poisson-Boltzmann predictions for counterion condensation on spheres. At high electric fields however, where ion advection is dominant, the electrophoretic mobility is enhanced significantly which we attribute to hydrodynamic stripping of the condensed layer of counterions from the surface of the particle.

Experimental and numerical investigation on a multi-layer protective structure under the synergistic effect of blast and fragment loadings

The main function of a multi-layer protective structure of a combatant ship is to prevent the inner cabins from being destroyed by anti-ship weapons. The damage effect of these weapons on ship structures mainly comes from the blast wave and fragments. The motivation of this study was to investigate the synergistic effect of blast wave and fragment impact loadings on the multi-layer protective structure. A protective structure model with four layers and a metal casing filled with TNT charge (MCTC) which was used to simulate the warhead of an anti-ship weapon were designed and manufactured. An experiment was conducted in which the MCTC exploded inside an empty cabin of the first layer of the multi-layer protective structure. The distribution of fragments and the equivalent bare charge of the MCTC were determined by a numerical method. From experimental results, the failure pattern of the multi-layer protective structure under the synergistic effect of blast wave and fragment impact loadings was presented. The synergistic effect for the stiffened plates was also presented in the experiment by comparing the deformation and the rupture of the air-backed and water-backed stiffened plates. On the other hand, the agreement between numerical results and experimental results validated the numerical method, which enabled the numerical model to be used to predict the response of a full scale structure under loadings of anti-ship weapons. Finally, a discussion of synergistic effects of blast and fragment loadings on a multi-layer structure was presented and suggestions for the design of a protective structure are put forward.

Beyond the Continuum: How Molecular Solvent Structure Affects Electrostatics and Hydrodynamics at Solid–Electrolyte Interfaces

Standard continuum theory fails to predict several key experimental results of electrostatic and electrokinetic measurements at aqueous electrolyte interfaces. In order to extend the continuum theory to include the effects of molecular solvent structure, we generalize the equations for electrokinetic transport to incorporate a space dependent dielectric profile, viscosity profile, and non-electrostatic interaction potential. All necessary profiles are extracted from atomistic molecular dynamics (MD) simulations. We show that the MD results for the ion-specific distribution of counterions at charged hydrophilic and hydrophobic interfaces are accurately reproduced using the dielectric profile of pure water and a non-electrostatic repulsion in an extended Poisson-Boltzmann equation. The distributions of Na(+) at both surface types and Cl(-) at hydrophilic surfaces can be modeled using linear dielectric response theory, whereas for Cl(-) at hydrophobic surfaces it is necessary to apply nonlinear response theory. The extended Poisson-Boltzmann equation reproduces the experimental values of the double-layer capacitance for many different carbon-based surfaces. In conjunction with a generalized hydrodynamic theory that accounts for a space dependent viscosity, the model captures the experimentally observed saturation of the electrokinetic mobility as a function of the bare surface charge density and the so-called anomalous double-layer conductivity. The two-scale approach employed here-MD simulations and continuum theory-constitutes a successful modeling scheme, providing basic insight into the molecular origins of the static and kinetic properties of charged surfaces, and allowing quantitative modeling at low computational cost.

An exact method to obtain effective electrostatic interactions from computer simulations: The case of effective charge amplification

We discuss here an exact method to determine the parameters regulating the screened Coulomb interactions among spherical macroions immersed in a simple electrolyte. This approach provides rigorous definitions for the corresponding screening length, effective permittivity, and renormalized charges, and can be employed for precise and reliable calculations of these parameters within any scheme. In particular, we introduce a simple procedure for extracting this information from computer simulations. The viability of this approach is demonstrated by applying it to a three-component model system which includes anionic nanoparticles and monovalent cations and anions. The mean forces between nanoparticles are determined directly from simulations with two macroions, plus small ions, inside a single cell with periodic boundary conditions. The values of the parameters of interest, on the other hand, are gathered from two separate sets of computer simulations: one set provides information about the short-range correlations among the small ions, which in turn determine the screening length and effective permittivity; the second set supplies the short-range components of the ionic distribution around one isolated macroion, which also determine its renormalized charge. The method presented here thus avoids the uncertain fitting of these parameters from the asymptotic tail of the mean force and allows us to investigate in detail this connection between the renormalized charge of the macroion and the short-range (virtual) part of the ionic cloud surrounding it. Using the standard prescription to extract an effective charge from the corresponding renormalized value, we then proceed to clarify the mechanisms behind the possibility of effective charge amplification (i.e., an effective charge larger than the bare macroion charge). Complementarily, we report results for the corresponding bridge functions too.

Effective charge of ionic microgel particles in the swollen and collapsed states: The role of the steric microgel-ion repulsion

In this work the system formed by charged (ionic) microgels in the presence of monovalent salt is investigated by solving numerically the Ornstein-Zernike integral equations within the Hypernetted-Chain approximation. The ionic density profiles, effective interaction between microgel particles, and the effective charge of the particles are calculated. In addition to the electrostatic interaction, the excluded-volume repulsion between the microgel particle and the ions is also explicitly taken into account. Although this steric interaction is irrelevant in the swollen state (when the packing fraction of the polymer network is low), it becomes a very important contribution close to the de-swollen state, hindering the counterion penetration inside the microgel mesh. The theoretical predictions indicate that the ionic density profiles are strongly affected by the degree of swelling, going from a volumetric distribution of counterions in the swollen state to a surface accumulation outside the particle that becomes more important as the particle shrinks. The electrostatic effective interaction between pairs of microgel particles is shown to be the result of a complex interplay between electrostatic and depletion effects that strongly depend on the bare charge density of the particle. For sufficiently charged microgel particles, the steric exclusion leads to a less efficient screening of the microgel charge near the de-swollen configuration, and so to a significant increase of the effective charge of the microgel particle.

Duality of two-dimensional field theory and four-dimensional electrodynamics leading to a finite value of the bare charge

We discuss the holographic duality consisting in the functional coincidence of the spectra of the mean number of photons (or scalar quanta) emitted by a point-like electric (scalar) charge in ()-space with the spectra of the mean number of pairs of scalar (spinor) quanta emitted by a point mirror in ()-space. Being functions of two variables and functionals of the common trajectory of the charge and the mirror, the spectra differ only by the factor (in Heaviside units). The requirement leads to unique values of the point-like charge and its fine structure constant, , , all their properties being as stated by Gell-Mann and Low for a finite bare charge. This requirement follows from the holographic bare charge quantization principle we propose here, according to which the charge and mirror radiations respectively located in four-dimensional space and on its internal two-dimensional surface must have identically coincident spectra. The duality is due to the integral connection of the causal Green's functions for ()- and ()-spaces and to connections of the current and charge densities in ()-space with the scalar products of scalar and spinor massless fields in ()-space. We discuss the closeness of the values of the point-like bare charge , the ‘charges’ and characterizing the shifts of the energy of zero-point electromagnetic oscillations in the vacuum by neutral ideally conducting surfaces of a sphere of radius and a cube of side , and the electron charge times . The approximate equality means that is the fine structure constant.

Renormalized Surface Charge Density for a Strongly Charged Plate in Asymmetric Electrolytes: Exact Asymptotic Expansion in Poisson Boltzmann Theory

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

Coarse-Grained Model for Predicting RNA Folding Thermodynamics

We present a thermodynamically robust coarse-grained model to simulate folding of RNA in monovalent salt solutions. The model includes stacking, hydrogen bond, and electrostatic interactions as fundamental components in describing the stability of RNA structures. The stacking interactions are parametrized using a set of nucleotide-specific parameters, which were calibrated against the thermodynamic measurements for single-base stacks and base-pair stacks. All hydrogen bonds are assumed to have the same strength, regardless of their context in the RNA structure. The ionic buffer is modeled implicitly, using the concept of counterion condensation and the Debye-Hückel theory. The three adjustable parameters in the model were determined by fitting the experimental data for two RNA hairpins and a pseudoknot. A single set of parameters provides good agreement with thermodynamic data for the three RNA molecules over a wide range of temperatures and salt concentrations. In the process of calibrating the model, we establish the extent of counterion condensation onto the single-stranded RNA backbone. The reduced backbone charge is independent of the ionic strength and is 60% of the RNA bare charge at 37 °C. Our model can be used to predict the folding thermodynamics for any RNA molecule in the presence of monovalent ions.

Effective electrostatic interactions arising in core-shell charged microgel suspensions with added salt

The mixture formed by charged (ionic) microgels in the presence of 1:1 added salt, with explicit consideration of a core-shell structure of the microgel particles, is studied. By solving numerically the three-component Ornstein-Zernike integral equations, the counter- and coion penetration inside the microgel network and the resulting effective microgel-microgel electrostatic interaction are calculated. This is done in the limit of very low microgel concentration, so that the resulting pair-wise effective potential is not affected by many-body particle-particle interactions. The ion-ion, microgel-ion, and microgel-microgel correlations are all treated within the Hypernetted-Chain approximation. The results obtained clearly show that the addition of salt to the microgel suspension has a deep impact on the screening of the bare charge of the particles, confirming an already well-known result: the strong reduction of the effective charge of the microgel occurring even for diluted electrolyte concentrations. We show that this effect becomes more important as we increase the shell size of the particle and derive a semi-empirical model for the effective charge as a function of the electrolyte concentration and the shell extension. The resulting microgel-microgel effective pair potential is analysed as a function of the shell extension and salt concentration. In all cases the interaction is a soft potential when particles overlap. For non-overlapping distances, our theoretical results indicate that microgel particles can be regarded as hard spherical colloids bearing an effective charge given by the net charge inside the particle and the microgel-microgel interaction shows a Yukawa-like behaviour as a function of the interparticle distance. It is also observed that increasing the bare-charge of the microgel induces a strong microgel-counterion coupling in the limit of very low electrolyte concentrations, which cannot be justified using linearized theories. This leads to an even more important adsorption of counterions inside the microgel network and to a reduction of the microgel-microgel effective repulsion.

A statistical description of explosion produced debris dispersion

The handling of explosives and ammunition introduces a safety risk for personnel and third parties. Accidents related to storage, transport and transshipment may result in severe injury and material damage. Dispersion of structural debris is one of the main hazards resulting from detonations inside structures. Reliable prediction models for debris dispersion are essential for risk assessment methods.In this article we give a statistical description of the dispersion of explosion produced debris. The basis is a general expression for the projectile areal number density in the horizontal and vertical plane. Combined with engineering models for the launch conditions, predictions can be made. An analytical solution to the equations of motion may be used to allow for fast calculations. A parameter study shows consistent results. The model has been validated with internal detonation tests of bare charges in reinforced concrete structures. The validation clearly shows the prediction capabilities of the model for three loading regimes described in the literature.We give a thorough description of the validity and limitations of the model, and an outlook of current and future research. Examples are the failing debris mass distribution prediction for reinforced concrete in the shock overloading regime, and ricochet and roll and break-up at impact phenomena.

Blast waves from cylindrical charges

Comparisons of explosives are often carried out using TNT equivalency which is based on data for spherical charges, despite the fact that many explosive charges are not spherical in shape, but cylindrical. Previous work has shown that it is possible to predict the over pressure and impulse from the curved surface of cylindrical charges using simple empirical formulae for the case when the length-to-diameter (L/D) ratio is greater or equal to 2/1. In this paper, by examining data for all length-to-diameter ratios, it is shown that it is possible to predict the peak over pressure, P, for any length-to-diameter ratio from the curved side of a bare cylindrical charge of explosive using the equation \(P=K_PM(L/D)^{1/3}/R^3\), where M is the mass of explosive, R the distance from the charge and \( K_P\) is an explosive-dependent constant. Further out where the cylindrical blast wave ‘heals’ into a spherical one, the more complex equation \(P=C_1(Z^{\prime \prime })^{-3}+C_2(Z^{\prime \prime })^{-2}+C_3(Z^{\prime \prime })^{-1}\) gives a better fit to experimental data, where \( Z^{\prime \prime } = M^{1/3}(L/D)^{1/9}/D\) and \(C_1,\, C_2 \) and \( C_3\) are explosive-dependent constants. The impulse is found to be independent of the L/D ratio.

Дуальность двумерной теории поля и четырёхмерной электродинамики, приводящая к конечному значению затравочного заряда

Дуальность двумерной теории поля и четырёхмерной электродинамики, приводящая к конечному значению затравочного заряда

Analytical modeling of bare surface barrier height and charge density in AlGaN/GaN heterostructures

In this paper, a physics based analytical model for the bare surface barrier height and two dimensional electron gas density in AlGaN/GaN heterostructures is presented. The model is based on simple charge neutrality electrostatics across the AlGaN barrier layer and that a low density of surface donor states is the source of the two dimensional electron gas. The model shows good agreement with reported experimental results.