Use Of Electric Fields Research Articles

A Comparison of Pulsed Electric Field Resistance for Three Microorganisms with Different Biological Factors in Grape Juice via Numerical Simulation

Pulsed electric field (PEF) is a promising nonthermal food preservation technology that is based on the use of electric field to eradicate spoilage and pathogenic microorganisms in food products. The effect of various biological factors on the transmembrane potential of different microorganisms (Staphyloccocus aureus, Escherichia coli DH5α, and Saccharomyces cerevisiae) was investigated by means of both numerical simulation and experimental method. The PEF resistance of different microorganisms in grape juice was compared by applying field strength of 12–24 kV/cm, treatment time of 30–180 μs, and an initial temperature of 30 oC. The results showed that S. cerevisiae exhibited the least resistance to PEF treatment, E. coli DH5α the second, and S. aureus the third. The simulation results indicated that larger cells like S. cerevisiae presented the higher values of transmembrane potential and induced field strength around the cells compared to E. coli DH5α and S. aureus, which led to a less resistance to PEF treatment. The effect of cell orientation on the induced transmembrane potential was very slight (1.67 % for E. coli DH5α and 3.43 % for S. cerevisiae). The thicker cell membrane caused concentrated electric field in the cell membrane, which enhanced the sensitivity of microorganism to PEF treatment. However, both transmembrane potential and electric field strength decreased with the thickness of cell wall increasing. According to both experimental and simulation results, it was evident that there was significant difference in the inactivation rate between different microorganisms, which could be largely attributed to the biological factors of different microorganisms.

Three-dimensional position and orientation measurements using magneto-quasistatic fields and complex image theory [measurements corner

Traditional wireless position-location systems, operating using propagating waves, suffer reduced performance in non-line-of-sight (NLoS) applications. Traditional systems that use quasistatic fields have instead been limited to short ranges, progressive direction-finding applications, require RF fingerprinting, or do not provide complete immunity to dielectric obstacles (use of electric fields). These limitations impose severe restrictions in applications such as tracking an American football during game play, where position and orientation tracking may be required over long ranges, and when the line-of-sight (LoS) is blocked by groups of people. A technique using magneto-quasistatic fields and complex image theory was recently shown to circumvent these problems, and to enable accurate long-range one-dimensional and two-dimensional measurements. In this work, we present three-dimensional position and orientation measurements using the magneto-quasistatic system and complex image theory over an area of 27.43 m × 27.43 m. Inverting the theoretical expression for the voltage measured at the terminals of the receiving loops to determine three-dimensional position and orientation resulted in mean and median geometric position errors of 0.77 m and 0.71 m, respectively; inclination orientation mean and median errors of 9.67° and 8.24°, respectively; and azimuthal orientation mean and median errors of 2.84° and 2.25°, respectively.

The Improvement of Dental Composite Properties with Electromagnetically Aligned Nanofiber

ABSTRACTBecause of the aesthetics, handy and low cost features, acrylic resin is the main material in denture fabrication last 40 years. The purpose of this study is to improve mechanical properties of acrylic based dental composites used in dentistry by applying nanofiber approaches. Polymethylmethacrylate (PMMA) is commonly used as a base acrylic denture material with benefits of rapid and easy handling but sometime this material can be fractured or cracked in clinical use because of the strength issues that is frequently used in restorative dentistry in recent years. A wide variety of fillers that are used to produce PMMA composites draw the attention in literature. Using PMMA composite resins with electrospun polyvinylalcohol (PVA) nanofiber fillers is our first novelty. Also the producing and using aligned electrospun fibers as a filler is our second novelty of this practice. PVA was selected as composite filler because of biocompatibility and preparing easily also has non-toxic solvent. Electrospinning system is manufactured that allows manipulation of electric field used in the application of alignment in lab scale. Various auxillary electrode systems are used for different patterns of alignment with the manufactured device and electrode systems produce fibers in different range of diameter. Scanning electron microscopy (SEM) is used for physical characterization and determined the range of fiber diameters. After the optimization of concentration step non-woven and aligned fibers are also analyzed. Non-woven fiber has no unique pattern because of the nature of electrospinning but aligned fibers has crossed lines. These produced fibers structured as layer-by-layer form with different features are used in producing PMMA dental composites with different volume ratios. In the last part of the research, PMMA dental composites are produced with aligned and formless fibers that are characterized with three-point bending test. The maximum flexural strength figure shows that fiber load by weight %0.25 and above improves the maximum. The change of flexural strength, elastic modulus values and toughness are obtained and compared with formless and aligned PVA nanofiber included composite specimens. As a result, mechanical properties of PMMA dental composites are improved with using PVA nanofibers as a filler also with the usage of aligned fibers instead of the formless ones the effects of improvement gets better with maximum values as 5.1 MPa (flexural strength), 0.8 GPa (elastic modulus), 170kJ/m3 (toughness).

Photocatalysts with internal electric fields

The photocatalytic activity of materials for water splitting is limited by the recombination of photogenerated electron-hole pairs as well as the back-reaction of intermediate species. This review concentrates on the use of electric fields within catalyst particles to mitigate the effects of recombination and back-reaction and to increase photochemical reactivity. Internal electric fields in photocatalysts can arise from ferroelectric phenomena, p-n junctions, polar surface terminations, and polymorph junctions. The manipulation of internal fields through the creation of charged interfaces in hierarchically structured materials is a promising strategy for the design of improved photocatalysts.

Electrostatically controlled large-amplitude, non-axisymmetric waves in thin film flows down a cylinder

AbstractWe examine the dynamics of a thin film flowing under gravity down the exterior of a vertically aligned inner cylinder, with a co-aligned, concentric cylinder acting as an outer electrode; the space between the outer cylinder and the film is occupied by an inviscid gas. The stability of the interface is studied when it is subjected to an electric field, applied by imposing a potential difference between the two cylinders. Leaky-dielectric theory is used in conjunction with asymptotic reduction, in the large-conductivity limit, to derive a single, two-dimensional evolution equation for the interfacial location, which accounts for gravity, capillarity, and electrostatic effects. A linear stability analysis is carried out which shows that non-axisymmetric modes become more dominant with increasing electric field strength. Our fully two-dimensional numerical solutions of the evolution equation demonstrate qualitative agreement between the trends observed in the nonlinear regime and those predicted by linear theory. These numerical solutions also show that, depending on the electric field strength and the relative proximity of the outer electrode, the interface either remains spatially uniform, or exhibits either axisymmetric or, importantly, non-axisymmetric travelling waves. The effect of wave formation on the interfacial area is investigated in connection with the use of electric fields to control thin film flows to enhance heat and mass transfer rates.

Electric control of magnetism in a multiferroic metal–organic framework

AbstractElectric control of magnetism is demonstrated in a multiferroic metal–organic framework with a perovskite structure. A moderate electric field of a few kV/cm applied during the cooling process is able to cause a large (more than 50%) change of the magnetization at low temperature. This significant magnetoelectric effect is ascribed to the electric field manipulation of orientation of hydrogen bonds that modify the superexchange interaction between metal ions.magnified imageElectric‐field cooling causes a large change in the magnetization of a multiferroic MOF.(© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Gate control of the electron spin-diffusion length in semiconductor quantum wells

The spin diffusion length is a key parameter to describe the transport properties of spin polarized electrons in solids. Electrical spin injection in semiconductor structures, a major issue in spintronics, critically depends on this spin diffusion length. Gate control of the spin diffusion length could be of great importance for the operation of devices based on the electric field manipulation and transport of electron spin. Here we demonstrate that the spin diffusion length in a GaAs quantum well can be electrically controlled. Through the measurement of the spin diffusion coefficient by spin grating spectroscopy and of the spin relaxation time by time-resolved optical orientation experiments, we show that the diffusion length can be increased by more than 200% with an applied gate voltage of 5 V. These experiments allow at the same time the direct simultaneous measurements of both the Rashba and Dresselhaus spin-orbit splittings.

Piezoelectric manipulation of Co/CoO exchange-bias bilayer system at low-temperature

The spintronics devices based on electric field is a key challenge today and the exchange bias effect is the basic structure used in these devices. We have studied the electric field control of annealed Co/CoO exchange bias system fabricated on the (011)-Pb(Mg1∕3Nb2∕3)O3-PbTiO3 piezoelectric substrate. The Co/CoO heterostructure was cooled down from above the Neel temperature (TN = 291 K) down to 15 K in the presence of electric and magnetic fields; the sample was cooled every time for each electric field measurement in order to avoid the training effect. The exchange bias effect was found to increase by 44% at the highest electric field value of 8 kV/cm measured at 15 K. The electric field tuning of exchange bias is attributed to the different magnetization reversal processes for left and right branches of magnetic hysteresis loop. Our results reinforce the possibility for the use of electric field as a tool to control the future spintronics devices.

Design parameters for voltage-controllable directed assembly of single nanoparticles

Techniques to reliably pick-and-place single nanoparticles into functional assemblies are required to incorporate exotic nanoparticles into standard electronic circuits. In this paper we explore the use of electric fields to drive and direct the assembly process, which has the advantage of being able to control the nano-assembly process at the single nanoparticle level. To achieve this, we design an electrostatic gating system, thus enabling a voltage-controllable nanoparticle picking technique. Simulating this system with the nonlinear Poisson–Boltzmann equation, we can successfully characterize the parameters required for single particle placement, the key being single particle selectivity, in effect designing a system that can achieve this controllably. We then present the optimum design parameters required for successful single nanoparticle placement at ambient temperature, an important requirement for nanomanufacturing processes.

Dielectrophoresis flow control in microchannels

Abstract The control of flow in microscale is one of the most important problems in microfluidic devices, which in particular, are used as micro heat exchangers. The use of electric field is one of the efficient methods of control of dielectric liquid flow in microscale. The electric field influences liquid flow by the EHD force which affects liquid behaviour in terms of the flow rate and pressure. The EHD force consists of three components: the first is the electrostatic force due to free charges present in the liquid, the next one is the force due to the gradient of permittivity of material, and the third one is caused by the change in the electric field intensity. The EHD force is used also in many commercial devices, for example EHD pumps or dielectrophoretic separators. An own approach to apply the EHD force to control the liquid flow rate is presented in this paper. Authors paid a close attention to the dielectrophoresis effect. Dielectric liquid in a non-uniform electric field tends to drift/migrate towards the region of high electric field intensity. With decreasing the electrode dimensions, the dielectrophoresis force becomes relatively stronger. For the dimensions under 400 μm the dielectrophoresis phenomenon can be used for control and actuation of the liquid flow in microchannels. The originally developed design of such flow controller is presented in this paper. The experimental investigations covered flow rate measurement of 2-propanol in microchannel flow controller with application of AC field. It was showed that the dielectrophoresis phenomenon could effectively control the flow. The results for distilled water are also comparatively discussed in the paper.

Comparing the pulsed electric field resistance of the microorganisms in grape juice: Application of the Weibull model

Pulsed electric field (PEF) technology is a nonthermal food preservation technology that is based on the use of electric field to eradicate microorganisms in foods. In present study, the PEF resistance of three strains of microorganisms (Staphyloccocus aureus, Escherichia coli DH5α and Saccharomyces cerevisiae) in grape juice was investigated by applying PEF treatments ranging from 9 kV/cm to 27 kV/cm and from 34 μs to 275 μs at an initial treatment temperature of 40 °C. The temperature measurement at particular locations in the processing line showed a general trend for all the composites: greater temperature increasing as the electric field strength and treatment time values increased. In all experimental conditions used in this investigation temperature increments were always lower than 8.8 °C. The obtained survival curves indicated that the inactivation of three strains increased with electric field strength and treatment time, or specific energy. The S. cerevisiae exhibited the least resistance to PEF treatments, S. aureus the second, E. coli DH5α the third. The experimental kinetics of inactivation by PEF of these microorganisms has been described by mathematical equations based on the modified Weibull model, using treatment time and specific energy as the control parameters. Both R2 and RMSE indicated a slightly higher degree of correlation between experimental and fitted values was achieved for models in terms of specific energy. Finally, the predicted inactivation curves from the established model were validated to evaluate the performance of the model using a total of 36 datasets for three microorganisms. Models built in terms of specific energy showed better accuracy than those in terms of treatment time. Whether treatment time or specific energy was used as control parameter of the model, all the bias factors ranged within the proposed acceptable limits. Overall, 80.6% and 85% of the mean prediction errors for above two models were in the acceptable prediction zone, more than 70% of which was considered as a threshold for a simulation model to provide acceptable predictions. The validation results indicated that the Weibull models were safe for predicting inactivation curves of S. aureus, E. coli DH5α and S. cerevisiae by PEF in grape juice. Therefore, the developed tertiary models were useful for assessing the lethal effects of different parameters on PEF treatment results and evaluating the relation between cost and benefit of a potential implementation of PEF technology in industrial production processes.

Active structuring of colloidal armour on liquid drops.

Adsorption and assembly of colloidal particles at the surface of liquid droplets are at the base of particle-stabilized emulsions and templating. Here we report that electrohydrodynamic and electro-rheological effects in leaky-dielectric liquid drops can be used to structure and dynamically control colloidal particle assemblies at drop surfaces, including electric-field-assisted convective assembly of jammed colloidal ‘ribbons’, electro-rheological colloidal chains confined to a two-dimensional surface and spinning colloidal domains on that surface. In addition, we demonstrate the size control of ‘pupil’-like openings in colloidal shells. We anticipate that electric field manipulation of colloids in leaky dielectrics can lead to new routes of colloidosome assembly and design for ‘smart armoured’ droplets.

HÁ ESPAÇO PARA A ESTIMULAÇÃO ELÉTRICA NERVOSA TRANSCUTÂNEA (TENS) COM MEIO DE INCENTIVO A REGENERAÇÃO NERVOSA PERIFÉRICA? UM ENSAIO TEÓRICO

Introdução: O uso de campos eletromagnéticos com o intuito de se incentivar a regeneração nervosa periférica vem sendo estudado principalmente desde a década de 80. Mutios meios de se administrar campos elétricos foram utilizados, tais como eletrodos implantados, estimulação intra operatória e eletrodos de agulha, porém existem poucos dados acerca do uso da estimulação elétrica com eletrodos de superfície (transcutânea). Por outro lado esta forma é usada muitas vezes para o controle da dor, sendo que em algumas delas há lesão nervosa periférica e degeneração Waleriana associada. Objetivos: O objetivo deste trabalho é apresentar as formas de se usar campos elétricos clinicamente com o objetivo de se promover a regeneração nervosa periféricas e discutir, dentro deste contexo, o uso da estimulação elétrica nervosa transcutânea. Métodos: Foi realizada uma revisão narrativa da literatura, incluindo trabalhos pré clínicos e clínicos sobre o uso de campos elétricos para se promover regeneração nervosa periférica, que tenham sido publicados em periódicos indexados no PubMed e Scielo, nas línguas portuguesa, inglesa, esponhala e francesa, no período de 1980 até 2012. Resultados e discussão: A grande maioria dos trabalhos encontrados são pré-clinicos, em camundongos e ratos. A estimulação peri-operatória ou com eletrodos implantados é a mais comum e somente um utilizou a estimulação elétrica nervosa transcutânea. Em geral os resultados apontam para um efeito positivo na regeneração nervosa periférica, mas os parâmetros de estimulação parecem ser críticos para os resultados, especialmente a frequência da corrente, o período de início do tratamento e o número de sessões de estimulação.

Finite-temperature decoherence of spin states in a {Cu3} single molecular magnet

We investigate the quantum evolution of spin states of a single molecular magnet in a local electric field. The decoherence of a {Cu3} single molecular magnet weakly coupled to a thermal bosonic environment can be analysed by the spin-boson model. Using the finite-temperature time-convolutionless quantum master equation, we obtain the analytical expression of the reduced density matrix of the system in the secular approximation. The suppressed and revived dynamical behaviour of the spin states are presented by the oscillation of the chirality spin polarization on the time scale of the correlation time of the environment. The quantum decoherence can be effectively restrained with the help of the manipulation of a local electric field and the environment spectral density function. Under the influence of the dissipation, the pointer states measured by the von Neumann entropy are calculated to manifest the entanglement property of the system–environment model.

Controlling Rashba spin splitting in Au(111) surface states through electric field

Combining density-functional theory (DFT) calculations and theoretical analyses, we demonstrate the high-order Rashba spin-orbit coupling in the Au(111) surface and the electric field manipulation of the Rashba splitting energy. A good linear relationship between the Rashba splitting energy and applied electric field is revealed by DFT calculations. The effect is attributed to the linear response of the first-order Rashba parameter to the applied electric field. The nonlinear relationship between Rashba splitting energy and the wave vectors identifies the higher-order Rashba components, which, however, are found to be less influenced by the external electric field. Our investigation provides an in-depth understanding of the tunability of Rashba splitting in a metal surface, which is of great interest in the area of electrical control of spin states.

Nano film processor based on the lateral self-oxidation of a nanoscale aluminum film

Electronic devices that are low in cost and capable of working without an external power supply are desirable for many applications. Conventional electronic circuits are based on semiconductors and the controlled transport of electrons and holes by electric field manipulation, diffusion, and injection. We describe electronic circuits based on the flow of femtoliter quantities of an electrolyte controlled by the lateral self-oxidation of a nanoscale aluminum film. The circuits provide basic functions such as clocks, electrical switches, pseudo transistors and display elements. The elements operate in a self-consuming mode and therefore do not require external power. They operate slowly over long periods of time and can form the basis of smart systems, smart labels, and many other applications.

Flow of clays

Recent experimental and theoretical research into physical phenomena in clays is reviewed. Clays’ present place in the context of modern materials science is briefly discussed, and illustrated through the rich behavior recently displayed in this physical model system. We will show that in order to understand macroscopic flow behaviors in these systems, it is crucial to know the underlying nanostructures in detail. With the clay nanostructural basis at hand, we will review recent advances in clay systems from the geological example of quick clay flows and avalanches, to materials science and the stability, strength and flow of smart electrorheological clay structures. In the case of natural quick clay, there is now hope of establishing a protocol for avalanche preditction based on rheological sample data. In materials science, the use of electric fields together with flow in order to improve the processing of clay composite materials may open new unexplored avenues. We will finally discuss that due to the interplay of van der Waals and electrostatic forces screened by ions at the nanoscale, clays may either form a glass, or a gel and thus give fundamental insights into the elusive questions related to materials universal aging flow dynamics.

The use of an electric field in the preparation of glass fibre/epoxy composites containing carbon nanotubes

This paper focuses on the use of electric field for the alignment of carbon nanotubes in glass fibre reinforced thermosetting composites and the associated infusion processing and property modifications. A satisfactory dispersion leads to high quality infusions with uniform distribution and infiltration of intrafibre microchannels by the nanofiller. Field application causes a reduction of resistivity during the process. The resistivity reduction follows an exponential decay with relaxation times in the 100–300s range. This process is attributed to preferential aggregation in the field direction, whilst indications of individual nanotube alignment are found. The through thickness conductivity of the composite increases by an order of magnitude with the application of the field reaching a value of 1.4×10−3S/m for 0.1wt.% nanotubes. The in plane conductivity remains unaffected. The interlaminar toughness increases slightly but statistically significantly upon the addition of nanotubes. A high field leads to a further increase of strain energy release rate to 520J/m2, which corresponds to a value 20% higher than the control. The effects observed on electrical properties are attributed mainly to preferential network formation in the field direction, whilst improvements in interlaminar toughness are linked to the nanotube alignment.

Analytical solutions and validation of electric field and dielectrophoretic force in a bio‐microfluidic channel

In a microbiological device, cell or particle manipulation and characterization require the use of electric field on different electrodes in several configurations and shapes. To efficiently design microelectrodes within a microfluidic channel for dielectrophoresis focusing, manipulation and characterization of cells, the designer will seek the exact distribution of the electric potential, electric field and hence dielectrophoresis force exerted on the cell within the microdevice. In this paper we describe the approach attaining the analytical solution of the dielectrophoretic force expression within a microchannel with parallel facing same size electrodes present on the two faces of channel substrates, with opposite voltages on the pair electrodes. Simple Fourier series mathematical expressions are derived for electric potential, electric field and dielectric force between two distant finite-size electrodes. Excellent agreement is found by comparing the analytical results calculated using MATLAB™ with numerical ones obtained by Comsol. This analytical result can help the designer to perform simple design parametric analysis. Bio-microdevices are also designed and fabricated to illustrate the theoretical solution results with the experimental data. Experiments with red blood cells show the dielectrophoretic force contour plots of the analytical data matched to the experimental results.

Nanotechnologies dedicated to nucleation control

This paper highlights the work of our group on the control and the observation of nucleation with techniques using nanotechnologies. This control is performed either by triggering nucleation in time with an external field or by localising it spatially in a microdroplet. Localisation in time using light irradiation induces nucleation by forming radicals; the use of electric field acts locally on the density of the solution. Localisation in space with a microfluidic device produces hundreds of nanovolume crystallisers where concentration and temperature are easily monitored. Thus, accurate statistical studies lead to the nucleation parameters (metastable zone, nucleation rate and polymorphism). Lastly, confinement with a microdroplet generator permits to reach very high supersaturations in fL to pL volumes allowing nucleation of a single crystal per microdroplet. All these methods clearly enhance nucleation in the metastable zone. Finally, they use small quantities of products offering potentialities for the screening of crystallisation conditions and phases (polymorphism).