Equal Charge Research Articles

Partially Annealed Disorder and Collapse of Like-Charged Macroions

Charged systems with partially annealed charge disorder are investigated using field-theoretic and replica methods. Charge disorder is assumed to be confined to macroion surfaces surrounded by a cloud of mobile neutralizing counterions in an aqueous solvent. A general formalism is developed by assuming that the disorder is partially annealed (with purely annealed and purely quenched disorder included as special cases), i.e., we assume in general that the disorder undergoes a slow dynamics relative to fast-relaxing counterions making it possible thus to study the stationary-state properties of the system using methods similar to those available in equilibrium statistical mechanics. By focusing on the specific case of two planar surfaces of equal mean surface charge and disorder variance, it is shown that partial annealing of the quenched disorder leads to renormalization of the mean surface charge density and thus a reduction of the inter-plate repulsion on the mean-field or weak-coupling level. In the strong-coupling limit, charge disorder induces a long-range attraction resulting in a continuous disorder-driven collapse transition for the two surfaces as the disorder variance exceeds a threshold value. Disorder annealing further enhances the attraction and, in the limit of low screening, leads to a global attractive instability in the system.

Attraction between negatively charged surfaces mediated by spherical counterions with quadrupolar charge distribution

We observed monoclonal antibody mediated coalescence of negatively charged giant unilamellar phospholipid vesicles upon close approach of the vesicles. This feature is described, using a mean field density functional theory and Monte Carlo simulations, as that of two interacting flat electrical double layers. Antibodies are considered as spherical counterions of finite dimensions with two equal effective charges spatially separated by a fixed distance l inside it. We calculate the equilibrium configuration of the system by minimizing the free energy. The results obtained by solving the integrodifferential equation and by performing the Monte Carlo simulation are in excellent agreement. For high enough charge densities of the interacting surfaces and large enough l, we obtain within a mean field approach an attractive interaction between like-charged surfaces originating from orientational ordering of quadrupolar counterions. As expected, the interaction between surfaces turns repulsive as the distance between charges is reduced.

Charge equalization circuit for discharging series‐connected batteries with regulated output

Charge equalization during the charging process has been extensively discussed for series‐connected batteries. However, charge inequality may also happen to batteries during discharging. The imbalance among batteries may result in over‐discharging and consequently damage to the batteries. To solve the problem, a balanced discharging method for a series‐connected battery bank is proposed. A flyback conversion circuit is designed with a pulse‐width‐modulation controller to achieve output voltage regulation as well as balanced discharging. The applicability of the proposed method is confirmed by experiments.

Equal charge black holes and seven-dimensional gauged supergravity

We present various supergravity black holes of different dimensions with some charges set equal in a simple, common form. Black hole solutions of seven-dimensional gauged supergravity with three independent angular momenta and two equal charges are obtained. We investigate the thermodynamics and the BPS limit of this solution, and find that there are rotating supersymmetric black holes without naked closed timelike curves. There are also supersymmetric topological soliton solutions without naked closed timelike curves that have a smooth geometry.

Conformation of preadsorbed polyelectrolyte layers on silica studied by secondary adsorption of colloidal silica

The conformation of cationic polyelectrolytes preadsorbed on macroscopic silica surfaces was studied before and after addition of colloidal silica (CS) and compared to the fixation capacity of CS. The study included two polyelectrolytes of equal charge density, cationic polyacrylamide and cationic dextran. Adsorbed amounts were determined with stagnation point adsorption reflectometry (SPAR) and quartz crystal microgravimetry (QCM). Unsaturated layers of polyelectrolyte were formed in SPAR by stopping the adsorption at a fractional coverage relative to saturation adsorption. These layers were probed by secondary saturation adsorption of colloidal silica (CS). At low salt concentrations a high fractional coverage of polyelectrolyte was required to attain adsorption of CS, while significant adsorption of CS was found also for low fractional coverages of polyelectrolyte at salt concentrations above 10 mM NaCl. Saturation adsorption of cationic polyacrylamide (CPAM) and cationic dextran (Cdextran) onto the silica surface was found to be similar, while the secondary adsorption of CS was significantly higher onto preadsorbed CPAM compared with Cdextran. The QCM and SPAR data together indicated that the adsorbed layer of Cdextran was thinner than CPAM, and that a loose, expanded layer was formed after adsorption of CS on CPAM but not on Cdextran.

Double-Tiered Switched-Capacitor Battery Charge Equalization Technique

The automobile industry is progressing toward hybrid, plug-in hybrid, and fully electric vehicles in their future car models. The energy storage unit is one of the most important blocks in the power train of future electric-drive vehicles. Batteries and/or ultracapacitors are the most prominent storage systems utilized so far. Hence, their reliability during the lifetime of the vehicle is of great importance. Charge equalization of series-connected batteries or ultracapacitors is essential due to the capacity imbalances stemming from manufacturing, ensuing driving environment, and operational usage. Double-tiered capacitive charge shuttling technique is introduced and applied to a battery system in order to balance the battery-cell voltages. Parameters in the system are varied, and their effects on the performance of the system are determined. Results are compared to a single-tiered approach. MATLAB simulation shows a substantial improvement in charge transport using the new topology. Experimental results verifying simulation are presented.

Influence of the overall charge and local charge density of pectin on the complex formation between pectin and β-lactoglobulin

The complex formation between β-lactoglobulin (β-lg) and pectin is studied using pectins with different physicochemical characteristics. Pectin allows for the control of both the overall charge by degree of methyl-esterification as well as local charge density by the degree of blockiness. Varying local charge density, at equal overall charge is a parameter that is not available for synthetic polymers and is of key importance in the complex formation between oppositely charged (bio)polymers. LMP is a pectin with a high overall charge and high local charge density; HMP B and HMP R are pectins with a low overall charge, but a high and low local charge density, respectively. Dynamic light scattering (DLS) titrations identified pH c, the pH where soluble complexes of β-lg and pectin are formed and pH ϕ, the pH of phase separation, both as a function of ionic strength. pH c decreased with increasing ionic strength for all pectins and was used in a theoretical model that showed local charge density of the pectin to control the onset of complex formation. pH ϕ passed through a maximum with increasing ionic strength for LMP because of shielding of repulsive interactions between β-lg molecules bound to LMP, while attractive interactions were repressed at higher ionic strength. Potentiometric titrations of homo-molecular solutions and mixtures of β-lg and pectin showed charge regulation in β-lg–pectin complexes. Around pH 5.5–5.0 the pK as of β-lg ionic groups are increased to induce positive charge on the β-lg molecule; around pH 4.5–3.5 the pK a values of the pectin ionic groups are lowered to retain negative charge on the pectin. Since pectins with high local charge density form complexes with β-lg at higher ionic strength than pectins with low local charge density, pectin with a high local charge density is preferred in food systems where complex formation between protein and pectin is desired.

Organic radical molecular solids based on [(TCNQ) n] − ( n=1 or 2): Syntheses, crystal structures, magnetic properties and DFT analyses

Four molecular solids consisting of the 7,7,8,8-tetracyanoquinodimethane (TCNQ) radical and benzylpyridinium or benzylquinolinium derivatives with molar ratios of 1:1 ( 1–3) and 2:1 ( 4) have been prepared and characterized. In the crystals of 1 and 3, TCNQ − monoanions and the corresponding cations form segregated stacks, which are regular in 1 but irregular in 3. Instead of segregated stacks, TCNQ − monoanions in 2 form isolated π-dimers. In the crystals of 4, two crystallographic independent TCNQ species possess almost equal fractional negative charge (ca. −0.5). Two types of TCNQ species form a tetrad, these tetrads make a TCNQ stack with the pattern …BAAB…BAAB… along the crystallographic a– b direction. The magnetisms for 1– 4 can be simply explained by the formation of singlet spin state. A broken symmetry approach in a density functional theory framework at the ub3lyp/6–31 g level was used to calculate the magnetic exchange constants in 1– 4. The results qualitatively demonstrate the observed magnetic properties.

Born-Infeld corrections to Coulombian interactions

Two-dimensional Born-Infeld electrostatic fields behaving as the superposition of two pointlike charges in the linearized (Maxwellian) limit are investigated by means of a nonholomorphic mapping of the complex plane. The changes in the Coulombian interaction between two charges in Born-Infeld theory are computed. Remarkably, the force between equal charges goes to zero as they approach each other.

Active charge balancing for Li-ion battery stacks

The Automotive System Engineering group of Infineon Technologies AG in Munich was assigned the task to develop an E-Cart — with the electrical features of a hybrid car driven by Lithium-ion (Li-ion) battery stack. he simple conventional solution — dissipating power for charge equalization will need to be replaced by an active energy shift between the cells. A fruitless search through the available literature — only basic principles have been published — forced the team to develop its own know-how. The resulting active system has much better performance at material costs comparable to a passive solution.

Magnetoconductivity and magnetoluminescence studies in bipolar and almost hole-only sandwich devices made from films of a π-conjugated molecule

We present magnetoconductivity and magnetoluminescence measurements in sandwich devices made from films of a π-conjugated molecule and demonstrate effects of more than 30 and 50% magnitude, respectively, in fields of 100 mT at room-temperature. It has previously been recognized that the effect is caused by hyperfine coupling, and that it is phenomenologically similar to other magnetic field effects that act on electron–hole pairs, which are well-known in spin-chemistry. However, we show that the very large magnitude of the effect contradicts present knowledge of the electron–hole pair recombination processes in electroluminescent π-conjugated molecules, and that the effect persists even in almost hole-only devices. Therefore, this effect is likely caused by the interaction of radical pairs of equal charge.

Ion-beam induced effects at 15 K in LiNbO3

In order to study the primary effects of the damage formation, LiNbO3z-cut crystals were irradiated at a temperature of 15K. The irradiation was done with 30keV H-, 50keV Li-, 160keV O- and 350keV Ar-ions at ion fluences between 5×1011 and 2×1017cm-2. To investigate the damage accumulation, Rutherford backscattering spectrometry (RBS) in channeling configuration was applied using 1.4MeV He-ions without warming the sample. The RBS measurements were performed in steps of equal charges providing a series of subspectra. It was observed that the backscattering yield of the damaged region decreases with increasing number of subspectra indicating an annealing of defects as a consequence of the RBS-measurement. The energy deposited into electronic processes by the analyzing He beam is mostly responsible for the observed defect annealing. The amount of annealing depends on the defect concentration and was taken into account for the calculation of the undisturbed defect accumulation for the different ion species.

Design of BEPCII bunch current monitor system

BEPCII is an electron-positron collider designed to run under multi-bunches and high beam current condition. The accelerator consists of an electron ring, a positron ring and a linear injector. In order to achieve the target luminosity and implement the equal bunch charge injection, the Bunch Current Monitor (BCM) system is built on BEPCII. The BCM system consists of three parts: the front-end circuit, the bunch current acquisition system and the bucket selection system. The control software of BCM is based on VxWorks and EPICS. With the help of BCM system, the bunch current in each bucket can be monitored in the Central Control Room. The BEPCII timing system can also use the bunch current database to decide which bucket needs to refill to implement ``top-off'' injection.

Phase and interference properties of optical vortex beams

Laguerre-Gauss vortex beams carrying different topological charges are generated from Hermite-Gauss laser beams emitted by a gas laser, and their phase properties are explored by studying their interference with a plane wave. Interference of two Laguerre-Gauss vortex beams carrying equal but opposite topological charge is also studied by using a modified Mach-Zehnder interferometer. Experimentally recorded intensity profiles are in good agreement with the theoretically expected profiles.

Gate bias stress effects due to polymer gate dielectrics in organic thin-film transistors

The operational stability of organic thin-film transistors (OTFTs) comprising bilayer polymer dielectric of poly(methylsilsesquioxane) (pMSSQ) and either the epoxy resin SU-8 or poly(4-vinyl phenol) was examined. Although not in direct contact with the semiconductor materials, the bottom dielectric layer did affect OTFT stability through water ion movement or charge injection inside the bottom dielectrics. In the comparison between our best polymer dielectric pMSSQ/SU-8 to the silicon oxide dielectric, the result emphasized that, at equal initial charge concentration, polymer dielectrics did not alleviate threshold-voltage shift but did maintain more stable current due to the lower gate capacitance than silicon oxide.

Structural and dynamical properties of a quasi-one-dimensional classical binary system

The ground state configurations and the ``normal'' mode spectra of a quasi-one-dimensional binary system of charged particles interacting through a screened Coulomb potential are presented. The minimum energy configurations were obtained analytically and independently through molecular dynamic simulations. A rich variety of ordered structures was found as a function of the screening parameter, the particle density, and the ratio between the charges of the distinct types of particles. Continuous and discontinuous structural transitions as well as an unexpected symmetry breaking in the charge distribution are observed when the density of the system is changed. For nearly equal charges, we found a disordered phase where a mixing of the two types of particles occurs. The phonon dispersion curves were calculated within the harmonic approximation for the one- and two-chain structures.

Effect of hydrolytic and oxidative enzymes produced by solid-state fermentation on greige linen fabric

Solid state fermentation (SSF) was applied for production of fungal enzyme preparations from Phanerochaete chrysosporium, Aspergillus oryzae, Aspergillus giganteus and Trichoderma virens using cotton seed-coat fragment waste as a carbon source and enzyme inducer. Lignin-holocellulose matrix of cotton seed coat fragment proved to be effective in inducing production of ligninolytic, cellulolytic and xylanolytic enzymes in solid-state fermentation. The effect of the enzymes produced by SSF on greige linen fabric is discussed and evaluated. In the first experiment the hydrolytic and accompanying oxidative enzymes in the buffer extract of the whole SSF cultures were used for fabric treatment. In the second trial, the enzymes produced in situ (whole SSF material—mixture of fungal biomass, residual substrate and enzymes) were used for the treatment. Weight loss, reducing sugar liberation and removal of colouring materials were measured. The results showed that at equal enzyme charges the intact SSF materials were more efficient than the enzyme extracts. Of the six strains evaluated, Ph. chrysosporium VKM F-1767 was the most effective in removing colouring matters from greige linen fabric.

Dominance and separability in posets, their application to isoelectronic species with equal total nuclear charge

We developed the dominance and separability degrees as two new mathematical tools measuring the amount of comparabilities and incomparabilities among pairs of disjoint subposets in a parent poset and we have related them through a theorem. Their mathematical properties when these measures are constrained to be higher than 0.5 have been studied. We have shown that variations of dominance and separability degrees from values in the real interval (0.5, 1] permit to “tune” the level of detail on the comparabilites and incomparabilities among the subsets studied. The lack of transitivity of dominance and separability degrees is established, along with the special requirement, needed on the poset, to have a transitivity of these measures. As a chemical application, the Hasse diagram of Born-Oppenheimer molecular total energies of the complete set of isoelectronic species with total nuclear charge 10 in their minimum energy configurations has been studied. We partition this set into 10 subsets, each one containing all the species with the same number of nuclei. By the calculation of the dominance and separability degrees a relation between the number of atoms in any ensemble and the Born-Oppenheimer energies is established.

Field‐theoretic simulations of polyelectrolyte complexation

Field‐theoretic simulations of polyelectrolyte complexation

Theoretical Investigations of the Dissociation of Charged Protein Complexes in the Gas Phase

A series of calculations, varying from simple electrostatic to more detailed semi-empirical based molecular dynamics ones, were carried out on charged gas phase ions of the cytochrome c(') dimer. The energetics of differing charge states, charge partitionings, and charge configurations were examined in both the low and high charge regimes. As well, preliminary free energy calculations of dissociation barriers are presented. It is shown that one must always consider distributions of charge configurations, once protein relaxation effects are taken into account, and that no single configuration dominates. All these results also indicate that in the high charge limit, the dissociation of protein complex ions is governed by electrostatic repulsion from the net charges, the consequences of which are enumerated and discussed. There are two main trends deriving from this, namely that charges will move so as to approximately maintain constant surface charge density, and that the lowest barrier to dissociation is the one that produces fragment ions with equal charges. In particular, it is shown that the charge-to-mass ratio of a fragment ion is not the key physical parameter in predicting dissociation products. In fact, from the perspective of the division of total charge, many dissociation pathways reported to be "asymmetric" in the literature should be more properly labelled as "symmetric" or "near-symmetric". The Coulomb repulsion model assumes that the timescale for charge transfer is faster than that for protein structural changes, which in turn is faster than that for complex dissociation.