High-intensity Electric Fields Research Articles

Steady-state crack growth along a grain boundary in interconnects with a high electric field intensity

Abstract A pre-existing microcrack is considered to grow in a steady state along a grain boundary of an interconnect line under the action of an applied electric field. Consistent with electromigration, the mechanism of crack growth is assumed via diffusive transport of atoms from both crack surfaces to the grain boundary. A set of second order nonlinear ordinary differential equations for the crack shape is derived from physical principles and solved numerically using the fourth-order Runge-Kutta method, coupled with a two-point shooting method. The results showed that the steady-state crack velocity V is proportional to the applied field E 0 with an exponent of 1.5, that is V = AE 1.5 0, in agreement with the previous analysis. However, the proportionality constant A is enhanced owing to electric field concentration at the crack tip.

Steady-state crack growth along a grain boundary in interconnects with a high electric field intensity

Abstract A pre-existing microcrack is considered to grow in a steady state along a grain boundary of an interconnect line under the action of an applied electric field. Consistent with electromigration, the mechanism of crack growth is assumed via diffusive transport of atoms from both crack surfaces to the grain boundary. A set of second order nonlinear ordinary differential equations for the crack shape is derived from physical principles and solved numerically using the fourth-order Runge-Kutta method, coupled with a two-point shooting method. The results showed that the steady-state crack velocity V is proportional to the applied field E 0 with an exponent of 1.5, that is V = AE 1.5 0, in agreement with the previous analysis. However, the proportionality constant A is enhanced owing to electric field concentration at the crack tip.

High electric field pulse pretreatment: potential for sugar beet processing

The application of high intensity electric field pulses (HELPs) on the cell disintegration of sugar beet cells was investigated. HELP treatment (20 pulses, ∼2.5 kV/ cm , 5 μF , 1–6 Hz) rapidly performed disintegration of sugar beet cell membranes in 20 s or less. In particular, field strength (1.2–2.5 kV/cm) and pulse number (1–200) had a key influence on the disintegration. Apart from the conventional thermal cell disintegration (at 75–80°C) followed by extraction, it is possible to extract sugar beet after HELP-pretreatment at ambient temperatures. HELP permeabilized sugar beet can be completely depleted of sucrose after one or two pressing steps (at 2 or 5 MPa, respectively) by adding water (less than 40% of the raw material weight) between the pressings. The HELP-treated and subsequently pressed pulp showed higher dry matter (∼30% dry matter) than the conventionally heat extracted and pressed pulp (∼15% dry matter) which provides a significant reduction in process time and energy requirement during dehydration of the extracted cossets.

Influence of high intensity electric field pulses and osmotic dehydration on the rehydration characteristics of apple slices at different temperatures

This study aimed to investigate the influence of pre-drying treatments (high intensity electric field pulses (HELP) with 20 pulses having 48 J/kg for 400 μs per pulse and osmotic dehydration (OD) in 50% sucrose solution) on some characteristics of rehydrated apples at different temperatures (24–90°C). Rehydration rate increased with temperature but higher rehydration capacity (RC) values were obtained at low temperatures (24°C and 45°C). RC of HELP treated + OD samples was 10–30% higher than the RC of the untreated + OD samples. Solid retention after rehydration was highest in HELP treated samples which also had firmer texture at full rehydration. Sugar gained during OD increased product firmness. Electrolyte release during rehydration was temperature dependent. The colour of the rehydrated apples darkened with increase in rehydration temperature and/or time.

Electrocaloric Effect in Some Perovskite Ferroelectric Ceramics and Multilayer Capacitors

Electrocaloric effect (ECE) of pure and modified PbSc 1/2 Ta 1/2 O 3 (PST) and its solid solutions and PbMg 1/3 Nb 2/3 O 3 - PbTiO 3 ferroelectric ceramics is studied at different temperatures and external electric field intensities. High value of (ECE) up to 2.3 K is observed in PST ceramics at modification in B sublattice by Co 3+ and Sb 5+ ions. The features of ECE in PST are explained by significant structure rearrangement at electric field induced Fm3m M R3m phase transition and high long range ordering of B ions in the ABO 3 perovskite structure. A further increase of ECE is observed in ceramic multilayer capacitors at higher electric field intensities up to 138 kV/cm.

A dynamic action potential model analysis of shock-induced aftereffects in ventricular muscle by reversible breakdown of cell membrane.

To elucidate the subcellular mechanism underlying the aftereffects of high-intensity dc shocks, a small pore, which mimics reversible breakdown of the cell membrane (electroporation), was incorporated into the phase-2 Luo-Rudy (L-R) model of ventricular action potentials. The pore size was set to occupy 0.15%-4.25% of the total cell membrane during the 10-ms shock. The pore was assumed to decrease after the shock exponentially with a time constant of 100-1,400 ms to simulate resealing process. In normal myocytes, the pore formation results in a delay of repolarization of the shocked action potential, which is followed by prolonged depolarization and oscillation of membrane potential like early afterdepolarization (EAD). Time- and voltage-dependent changes in the delayed rectifier K+ currents (IKr, IKs) in combination with those of L-type Ca2+ current (ICa,(L)) and ion flux through the pore (I(pore)) are responsible for the potential changes. Spontaneous excitation from the oscillation depends on activation of ICa,(L). In myocytes overloaded with Na+ and Ca2+ secondary to 90% inhibition of Na+-K+ pump, the pore formation results in a delay of repolarization of the shocked action potential, which is followed by slower cyclic depolarization in response to spontaneous release of Ca2+ from the sarcoplasmic reticulum (SR). This delayed afterdepolarization-type oscillation is abolished by complete block of Ca2+ release from the SR. These findings suggest that high-intensity electric field application will cause arrhythmogenic responses through a transient rupture of sarcolemma with different subcellular events in ventricular cells under normal and pathological conditions.

Effects of pretreatments on the diffusion kinetics and some quality parameters of osmotically dehydrated apple slices.

This study compared mass transfer during osmotic dehydration (OD) and some quality indices of untreated apple slices to those of apple slices pretreated by either blanching, freezing, or applying high-intensity electric field pulses (HELP) or high pressure (HP). HP, HELP, and blanching increased water loss. Untreated and HELP-treated samples had comparable solids gains, which were lower (P < 0.05) than in the other samples. Apple slices turned brown after pretreatment but the L values of these samples increased with OD. The breaking force of dried samples increased with OD time, and pretreated samples had firmer dried texture than the untreated. Vitamin C content decreased with OD time, but HP- and HELP-treated apples had better retention of vitamin C.

Ion field emission from micrometer-sized spherical glass grains

An experimental investigation of ion field emission from spherical glass grains in a 1-10 /spl mu/m size range is described. A single dust grain is trapped in an electrodynamic quadrupole and charged positively by a monoenergetic ion beam. The energy of these ions (5 keV) results in a high surface potential and high electric field intensity. A limitation of the surface potential due to ion field emission was observed for the surface field intensity of 3/spl times/10/sup 8/ V/m, which is a considerably lower value than expected. The density of the discharging current was as high as 10/sup -5/ A/m/sup 2/, and increased exponentially with increasing intensity of the electric field. As there are no data of the ion field emission from insulators, we have used the zinc grains for a comparison. Taking into account the irregular shape of used metallic grains, we conclude that the ion field emission from the glass grains starts at a significantly (two orders of magnitude) lower electric field intensity than that from metals. This may lead to the limitation of the attainable surface potential of small insulator grains. The possible effect of the ion field emission on the charging of dust grains in the interplanetary space is discussed.

Effects of high hydrostatic pressure or high intensity electrical field pulse pre-treatment on dehydration characteristics of red paprika

The effects of various pre-treatments (hot water blanching, skin treatments, high pressure and high intensity electric field pulse treatment) on the dehydration characteristics of red paprika ( Capsicum annuum L.) were evaluated and compared with untreated samples. Hot water blanching (100°C, 3 min) prior to dehydration (fluidised bed dryer at 60°C, 6 h and 1 m/s) resulted in the permeabilisation of 88% of the cell membranes in paprika, which in turn resulted in a higher mass and heat transfer. Skin treatments (such as lye peeling and acid treatment), as practised conventionally, increased dehydration rates but affected only the skin permeability. The application of high hydrostatic pressure (HHP, 400 MPa for 10 min at 25°C) or high intensity electric field pulses (HELP, 2.4 kV/cm, pulse width 300 μs, 10 pulses, pulse frequency 1 Hz) pre-treatments resulted in cell disintegration indexes of 0.58 and 0.61, respectively. Cell permeabilisation of these physical treatments resulted in higher drying rates, as well as higher mass and heat transfer coefficients, as compared to conventional pre-treatments.

Processing concepts based on high intensity electric field pulses

Emerging non-thermal food processing techniques are receiving considerable attention. This is because of their potential for quality and safety improvement of our food supply, for the ability to enhance conventional processing operations or to create alternative ones, as well as modify existing or non-conventional raw materials, food constituents or processed foods. High intensity electric field pulse technology is one of the most advanced emerging non-thermal processing methods and is currently undergoing intensive scientific and developmental evaluation. The objectives of this review are to summarize and identify the key advantages of this emerging technology and to convert it into optimum use. Those attempts are a combination of research on a kinetic basis and on a cellular level and the subsequent transfer of the knowledge gained into pilot scale.

One model of electric conduction and electric field distributions in a liquid insulator

The electric properties of the liquid insulator have been studied in this work. We have described the time-dependent model of the conduction processes in the liquid insulator under high voltages. Our model is a generalization of the Frenkel conduction model. (The last deals only with stationary conduction processes). Calculation of the electric field has also been made for two types of problems: (1) the external electric field applied to a liquid, is created by plane electrodes. (2) A spherical electrode of a small size creates it. The electrodes are assumed to be under constant high voltage. There is no electron emission or ion injection from the electrodes. But the field intensity influences on the molecular dissociation rate, and this fact has been taken into account. We have shown that the space charge, which arises under conditions mentioned above gives rise to changes in the electric field distribution. The model on hand is also used for calculating the hydrodynamic phenomena under high non-uniform electric field intensities. It has also been shown that the velocity of the strong EHD flows is proportional to the value of direct current or the squared value of applied voltage.

Electrodispersion for Supercritical CO2−Water Phase Contact

Supercritical carbon dioxide is a preferred solvent substitute in the chemical process industries, but processing that requires contact between CO2 and an aqueous phase has been hindered by the inefficient phase contact and high capital cost of conventional contactors. We examine the phase-contact performance of an electrodispersion contactor in this service. We have dispersed droplets of aqueous phases into supercritical CO2 using pulsed, high-intensity electric fields. Using small-angle laser light scattering, we characterized the mean droplet size as a function of operating conditions (liquid flow rate, field strength, frequency, temperature, and pressure) and observed operating regions that yield submicron-sized droplets. The effects of temperature and pressure on droplet size were correlated with the interfacial tension. Then, using the extraction of ethanol from a water−ethanol solution as a test system, we attempted to characterized mass transfer performance, but under maximum CO2 flow rate conditions of the downstream liquid condensers, mass transfer was equilibrium-limited in all cases. Because of the small droplet size and high interfacial area, the electrodispersion contactor offers the potential for achieving excellent mass transfer performance. The submicron-sized droplets were efficiently coalesced electrostatically, and negligible entrainment was observed. We anticipate that initial commercial applications might arise in the processing of small volumes of high-value substances in aqueous media such as might be found, for instance, in the pharmaceutical industry.

Temperature dependence of the ionization coefficients of Al/sub x/Ga/sub 1-x/As

As Al/sub x/Ga/sub 1-x/As alloys are increasingly used for microwave and millimeter wave power devices and circuits that work under high electric field intensities and junction temperatures; understanding the temperature dependence of impact ionization and related properties in this material system becomes more and more important. Measurements of the multiplication gain and noise of avalanche photodiodes (APDs) provide insight to the avalanche characteristics of semiconductors. Previously, we have reported the characteristics of GaAs and Al/sub 0.2/Ga/sub 0.8/As APD's at room temperature. In this paper, the gain and noise of a series of homojunction Al/sub x/Ga/sub 1-x/As APD's were investigated over a wide temperature range from 29/spl deg/C to 125/spl deg/C, and the temperature dependence of their ionization coefficients was extracted.

Impact of high intensity electric field pulses on cell permeabilisation and as pre-processing step in coconut processing

The impact of high intensity electric field pulses (HELP) for cell permeabilisation of coconut was studied. A preliminary investigation of suitable field strength and total energy input for HELP treatment (field strength, 0.1–2.5 kV/cm, number of pulses, 0–200, pulse width, 575 μs and pulse frequency 1 Hz) was carried out. A comparison of the HELP process ( E=2.5 kV/cm, n=20 pulses, t=575 μs and frequency 1 Hz) was made with other methods of cell disintegration (e.g. mechanical rupture, thermal treatment, freeze-thaw cycle) on the yield of coconut milk obtained and its protein and fat contents. A combination of HELP treatment and centrifugation (10 000× g for 10 min) was employed as pre-processing step prior to coconut dehydration in a fluidised bed dryer (60°C, air velocity 1 m/s) in an attempt to enhance drying rates. Treatment with HELP under suitable conditions ( E=2.5 kV/cm, n=20 pulses, t=575 μs and frequency 1 Hz) resulted in 20% increase in milk yield with reference to the untreated samples. The fat contents of the extracted milk from HELP treated and untreated samples were 58.0% and 61.2%, respectively, and the corresponding protein contents of the aqueous medium after separation by centrifugation were 50.0% and 51.6%. The combination of HELP and centrifugation step resulted in a reduction of approximately 22% of the drying time as compared to the untreated samples which could be of advantage in the production of copra.

Electrically induced changes in polymer dispersed liquid crystals

This letter reports the changes induced in polymer dispersed liquid crystal films by applying high intensity electric fields (charge process). It has been observed that lower reorientation fields and sharper OFF–ON transitions characterize samples after the charge process. Scanning electron microscopy and dielectric investigation show that the charge process induces both a morphology and a dielectric variation in films. Nevertheless a reduction in the surface anchoring energy of the liquid crystal at droplet interface has been postulated as the changes in the dielectric properties and droplet size cannot entirely justify the enhancement of electro-optical properties. The role played by the temperature at which the charge process is performed is also discussed.

High Intensity Pulsed Electric Fields Applied to Egg White: Effect on Salmonella Enteritidis Inactivation and Protein Denaturation

High-intensity electric fields have been successfully applied to the destruction of Salmonella Enteritidis in diaultrafiltered egg white. The effects of electric field strength (from 20 to 35 kV·cm−1), pulse frequency (from 100 to 900 Hz), pulse number (from 2 to 8), temperature (from 4 to 30°C), pH (from 7 to 9), and inoculum size (from 103 to 107 CFU·ml−1) were tested through a multifactorial experimental design. Experimental results indicate that, for Salmonella inactivation, the electric field intensity is the dominant factor with a strongly positive effect, strengthened by its positive interaction with pulse number. Pulse number, temperature, and pH have also significant positive effects but to a lesser extent. In the most efficient conditions, the pulsed electric field (PEF) treatment is capable of 3.5 log10 reduction in viable salmonellae. Simultaneously, the measure of surface hydrophobicity does not indicate any increase after PEF treatment. These results suggest that no protein denaturation occurs, unlike what is observed after comparable heat treatment in terms of Salmonella inactivation (55°C for 15 min).

Accelerated Mass Transfer During Osmotic Dehydration of High Intensity Electrical Field Pulse Pretreated Carrots

ABSTRACTHigh intensity electrical field pulse (0.22 to 1.60 kV/cm) pretreatment was tested to accelerate the osmotic dehydration of carrot. Applied energy in the range of 0.04 to 2.25 kJ/kg, increased cell disintegration index in the range of 0.09 to 0.84 with &lt; 1 °C rise in the product temperature. The effective diffusion coefficients of water and solute, determined using a Fickian diffusion model, increased exponentially with electric field strength according to D = A exp(‐B/E). The rise in effective diffusion coefficient may be attributed to an increase in cell wall permeability, facilitating transport of water and solute. Such increase was evidenced by cell disintegration index and softening of product.

Novel approaches in food-processing technology: new technologies for preserving foods and modifying function.

Recent advances in emerging food-processing technologies, such as high hydrostatic pressure or high-intensity electric field pulses, allow targeted and sophisticated modification and preservation of foods. We are beginning to understand the mechanisms involved in pressure inactivation of bacterial spores and have been collecting considerable amounts of kinetic data regarding inactivation mechanisms of enzymes and vegetative microorganisms. We are also gaining more insight into the permeabilization of plant membranes and related biosynthetic responses, making progress in food structure engineering and food modification for function, and have been initiating process developments for gentle processing of delicate biomaterials based on pressure-assisted phase transitions of water.

Transmission electron microscopy of Listeria innocua treated by pulsed electric fields and nisin in skimmed milk

Pulsed electric fields (PEF) is a nonthermal food preservation process where organoleptic and nutritional properties of the food are maintained. PEF is known to inactivate microorganisms by causing dielectric breakdown of the cell membrane, thus altering the functionality of the membrane as a semipermeable barrier. The extent of damage of the cell membrane, whether visible in the form of a pore or as loss of membrane functionality leads to the inactivation of the microorganism. The objective of this study was to investigate under transmission electron microscopy (TEM) the morphological changes on Listeria innocua as a result of PEF treatment in skimmed milk containing nisin. L. innocua was subjected to PEF at selected electric field intensities of 30, 40, and 50 kV/cm. L. innocua was treated by PEF in both skimmed milk with and without 37 IU nisin/ml. L. innocua treated by PEF in skimmed milk exhibited an increase in the cell wall roughness, cytoplasmic clumping, leakage of cellular material, and rupture of the cell walls and cell membranes. L. innocua subjected to PEF in skimmed milk containing 37 IU nisin/ml exhibited an increased cell wall width. At the highest electric field intensity, 50 kV/cm, elongation of the cell length was observed. There were no morphological differences between cells treated by PEF in skimmed milk with or without nisin. The combination of PEF and nisin exhibit an additive effect in the morphological damage observed on L. innocua. Pore formation was observed on L. innocua for an electric field intensity of 40 kV/cm. The inactivation of L. innocua was a consequence of rupture of the cell membrane and loss of cell membrane functionality.

Resistivity of red blood cells against high-intensity, short-duration electric field pulses induced by chelating agents.

The interaction of human red blood cells (RBCs) with diethylenetriamine-pentaacetic acid (DTPA) or its Gd-complex (Magnevist, a widely used clinical magnetic resonance contrast agent containing free DTPA ligands) led to the following, obviously interrelated phenomena. (i) Both compounds protected erythrocytes against electrohemolysis in isotonic solutions caused by a high-intensity DC electric field pulse. (ii) The inhibition of electrohemolysis was observed only when cells were electropulsed in low-conductivity solutions. (iii) The uptake of Gd-DTPA by electropulsed RBCs was relatively low. (iv) (Gd-) DTPA reduced markedly deformability of erythrocytes, as revealed by the electrodeformation experiments using high-frequency electric fields. Taken together, the results indicate that (Gd-) DTPA produce stiffer erythrocytes that are more resistant to electric field exposure. The observed effects of the chelating agents on the mechanical properties and the electropermeabilization of RBCs must have an origin in molecular changes of the bilayer or membrane-coupled cytoskeleton, which, in turn, appear to result from an alteration of the ionic equilibrium (e.g., Ca(2+) sequestration) in the vicinity of the cell membrane.