Terms Of Field Strength Research Articles

Pulsed electric fields-assisted extraction of valuable compounds from red grape pomace: Process optimization using response surface methodology.

The application of Pulsed electric fields as a mild and easily scalable electrotechnology represents an effective approach to selectively intensify the extractability of bioactive compounds from grape pomace, one of the most abundant residues generated during the winemaking process. This study addressed the optimization of the pulsed electric fields (PEF)-assisted extraction to enhance the extraction yields of bioactive compounds from red grape pomace using response surface methodology (RSM). The cell disintegration index (Z p ) was identified as response variable to determine the optimal PEF processing conditions in terms of field strength (E = 0.5-5 kV/cm) and energy input (WT = 1-20 kJ/kg). For the solid-liquid extraction (SLE) process the effects of temperature (20-50°C), time (30-300min), and solvent concentration (0-50% ethanol in water) on total phenolic content (TPC), flavonoid content (FC), total anthocyanin content (TAC), tannin content (TC), and antioxidant activity (FRAP) of the extracts from untreated and PEF-treated plant tissues were assessed. The phenolic composition of the obtained extracts was determined via HPLC-PDA. Results demonstrated that the application of PEF at the optimal processing conditions (E = 4.6 kV/cm, WT = 20 kJ/kg) significantly enhanced the permeabilization degree of cell membrane of grape pomace tissues, thus intensifying the subsequent extractability of TPC (15%), FC (60%), TAC (23%), TC (42%), and FRAP values (31%) concerning the control extraction. HPLC-PDA analyses showed that, regardless of the application of PEF, the most abundant phenolic compounds were epicatechin, p-coumaric acid, and peonidin 3-O-glucoside, and no degradation of the specific compounds occurred upon PEF application. The optimization of the PEF-assisted extraction process allowed to significantly enhance the extraction yields of high-value-added compounds from red grape pomace, supporting further investigations of this process at a larger scale.

Optimization of Pulsed Electric Fields-Assisted Extraction of Phenolic Compounds From White Grape Pomace Using Response Surface Methodology

This study was focused on the optimization of the pulsed electric fields (PEF)-assisted extraction process using central composite design for response surface methodology from response surface methodology (RSM) with the aim to sustainably intensify the extractability of phenolic compounds from white grape pomace. The cell disintegration index (Zp) was used as response variable to identify the optimal PEF pre-treatment conditions of grape pomace in terms of field strength (E = 0.5–5 kV/cm) and energy input (WT = 1–20 kJ/kg), to be applied prior to the subsequent solid-liquid extraction (SLE) process. for both untreated and PEF-treated samples SLE process was optimized to determine the most effective combination of extraction temperature (20–50°C), extraction time (30–300 min), and solvent concentration (0–100% ethanol in water). Total phenolic content (TPC), flavonoid content (FC), and antioxidant activity (FRAP) of the obtained extracts were determined. The extracted compounds from untreated and PEF-treated samples at the optimal conditions were analyzed via HPLC-PDA analysis. Results revealed that, at a fixed extraction temperature (50°C), the application of PEF at optimal processing conditions (E = 3.8 kV/cm, WT = 10 kJ/kg) prior to SLE has the potential to reduce the solvent consumption (3–12%) and shorten the extraction time (23–103 min) to obtain the same recovery yield of phenolic compounds. Under optimized conditions, the extracts derived from PEF-treated samples showed significantly higher TPC (8%), FC (31%), and FRAP (36%) values, as compared to the control extraction. HPLC analyses revealed that epicatechin, p-coumaric acid, and quercetin were among the main phenolic compounds extracted, and no degradation phenomena occurred due to PEF application.

Efficient ULF Transmission Utilizing Stacked Magnetic Pendulum Array

A novel stacked magnetic pendulum array (MPA) is proposed as an antenna for efficient transmission in ultralow frequencies (ULF). The MPA structure consists of an array of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${m\times n}$ </tex-math></inline-formula> magnets stacked in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> rows (m magnets of the same magnetization per row) and a solenoid that encompasses the array. The magnetic flux generated by the solenoid couples to the magnets through a mechanical motion and creates a strong time variant magnetic field at the resonance frequency of the array. The proposed MPA is developed utilizing bearings with extremely small damping which hold the magnets, enable efficient oscillation, and guarantees a high-quality factor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> -factor). A comprehensive analysis to study the performance of the MPA and a conventional solenoid will be provided and accordingly, characteristics of an arbitrary <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${m\times n}$ </tex-math></inline-formula> array in terms of field strength, resonance frequency, transmission efficiency and inductance are studied. Furthermore, a figure of merit (FOM) is introduced as the ratio of efficiency to the maximum linear dimension of the antenna. The experimental results for a fabricated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5 \times 11$ </tex-math></inline-formula> array show a resonance frequency of 715 Hz and a Q-factor of 94 while the maximum linear dimension of the antenna is just 9 cm. Moreover, measurement results show 24.9 dB improvement in the transmission efficiency of the MPA compared to the efficiency of a single solenoid of the same dimensions. The MPA has the FOM of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1.26\times 1}{0}^{{4}}$ </tex-math></inline-formula> which is noticeably higher than that of proposed antennas in the literature. To demonstrate broadband transmission with the MPA, a binary frequency shift keying (BFSK) signal is transmitted through the use of direct antenna modulation (DAM) at a rate of 18 bps.

A new gauge-invariant double copy for heavy-mass effective theory

We propose a new form of the colour-kinematics/double-copy duality for heavy-mass effective field theories, which we apply to construct compact expressions for tree amplitudes with heavy matter particles in Yang-Mills and in gravity to leading order in the mass. In this set-up, the new BCJ numerators are fixed uniquely and directly written in terms of field strengths, making gauge invariance manifest. Furthermore, they are local and automatically satisfy the Jacobi relations and crossing symmetry. We construct these BCJ numerators explicitly up to six particles. We also discuss relations of the BCJ numerators in the heavy-mass effective theory with those in pure Yang-Mills amplitudes.

Massive Measurements of 5G Exposure in a Town: Methodology and Results

We target the problem of performing a large set of measurements over the territory to characterize the exposure from a 5G deployment. Since using a single Spectrum Analyzer (SA) is not practically feasible (due to the limited battery duration), in this work we adopt an integrated approach, based on the massive measurement of 5G metrics with a 5G smartphone, followed by a detailed analysis done with the SA and an ElectroMagnetic Field (EMF) meter in selected locations. Results, obtained over a real territory covered by 5G signal, reveal that 5G exposure is overall very limited for most of measurement locations, both in terms of field strength (up to 0.7 [V/m]) and as share w.r.t. other wireless technologies (typically lower than 15%). Moreover, our approach allows easily spotting measurement outliers, e.g., due to the exploitation of Dynamic Spectrum Sharing (DSS) techniques between 4G and 5G. In addition, the exposure metrics collected with the smartphone are overall a good proxy of the total exposure measured over the whole 5G channel. Moreover, the sight conditions and the distance from 5G base station play a great role in determining the level of exposure. Finally, a maximum of 130 [W] of power radiated by a 5G base station is estimated in the scenario under consideration.

Carrier Distribution Control in van der Waals Heterostructures of MoS2 and WS2 by Field-Induced Band-Edge Engineering

The electronic properties of van der Waals heterostructures composed of ${\mathrm{Mo}\mathrm{S}}_{2}$ and ${\mathrm{WS}}_{2}$ under a perpendicular electric field are studied in terms of field strength, electron doping concentration, and interlayer stacking arrangement based on the density-functional theory. The calculation results show that accumulated carrier distribution can be controlled by tuning the field direction, field strength, and doping concentration. The electron is localized on the ${\mathrm{Mo}\mathrm{S}}_{2}$ layer on the positively charged electrode side under a strong positive field with a low doping concentration, whereas they are extended throughout both the ${\mathrm{Mo}\mathrm{S}}_{2}$ and ${\mathrm{WS}}_{2}$ layers under a strong negative field. Stacking misorientation between the layers further enhances the electron localization under a positive field and delocalization under a strong negative field. The stacking arrangement and electric field allow additional tuning of the electronic properties of van der Waals heterostructures.

Impact of Spin Torque Oscillator Frequency in Microwave-Assisted Magnetic Recording

In this article, we present a systematic modeling investigation for some important physical insights in microwave-assisted magnetic recording (MAMR). Specifically, the characteristics of the effective write field in the presence of the ac field generated by the embedded spin torque oscillator (STO) is analyzed in terms of field strength and field-gradient gain for recording, as well as the enhancement of reverse erasure field. It is found that the rotating frequency of the field generating layer (FGL) of the STO plays a very important role. The effective write field enhancement for both recording and erasure due to the rotating ac field increase with increasing the ac field frequency with a rate close to 1 T per 28 GHz. Either the recording field gain or erasure field enhancement rolls off at high frequencies. The roll-off frequency for the recording field gain is significantly higher, approximately 20 GHz, than that for erasure field enhancement, leaving a broader frequency range for the ac field over which substantial gains for the recording field strength and gradients can be obtained while avoiding any erasure field enhancement. The understanding also provides guidelines for both head and media designing.

N=2 super Yang-Mills theory in projective superspace

We find a formulation of $\mathcal{N}=2$ supersymmetric Yang-Mills theory in Projective superspace. In particular we find an expression for the field strength in terms of an unconstrained prepotential which is desirable when quantizing the theory. We use this to write the action in terms of the prepotential and show that it reduces to the known result in the abelian limit.

Remote magnetic actuation using a clinical scale system.

Remote magnetic manipulation is a powerful technique for controlling devices inside the human body. It enables actuation and locomotion of tethered and untethered objects without the need for a local power supply. In clinical applications, it is used for active steering of catheters in medical interventions such as cardiac ablation for arrhythmia treatment and for steering of camera pills in the gastro-intestinal tract for diagnostic video acquisition. For these applications, specialized clinical-scale field applicators have been developed, which are rather limited in terms of field strength and flexibility of field application. For a general-purpose field applicator, flexible field generation is required at high field strengths as well as high field gradients to enable the generation of both torques and forces on magnetic devices. To date, this requirement has only been met by small-scale experimental systems. We have built a highly versatile clinical-scale field applicator that enables the generation of strong magnetic fields as well as strong field gradients over a large workspace. We demonstrate the capabilities of this coil-based system by remote steering of magnetic drills through gel and tissue samples with high torques on well-defined curved trajectories. We also give initial proof that, when equipped with high frequency transmit-receive coils, the machine is capable of real-time magnetic particle imaging while retaining a clinical-scale bore size. Our findings open the door for image-guided radiation-free remote magnetic control of devices at the clinical scale, which may be useful in minimally invasive diagnostic and therapeutic medical interventions.

Implications of quantum ambiguities in k=1 loop quantum cosmology: Distinct quantum turnarounds and the super-Planckian regime

The spatially closed Friedmann-Lema\^{i}tre-Robertson-Walker model in loop quantum cosmology admits two inequivalent consistent quantizations: one based on expressing the field strength in terms of the holonomies over closed loops, and, another using a connection operator and open holonomies. Using the effective dynamics, we investigate the phenomenological differences between the two quantizations for the single fluid and the two fluid scenarios with various equations of state, including the phantom matter. We show that a striking difference between the two quantizations is the existence of two distinct quantum turnarounds, either bounces or recollapses, in the connection quantization, in contrast to a single distinct quantum bounce or a recollapse in the holonomy quantization. These results generalize an earlier result on the existence of two distinct quantum bounces for stiff matter by Corichi and Karami. However, we find that in certain situations two distinct quantum turnarounds can become virtually indistinguishable. And depending on the initial conditions, a pure quantum cyclic universe can also exist undergoing a quantum bounce and a quantum recollapse. We show that for various equations of states, connection based quantization leads to super-Planckian values of the energy density and the expansion scalar at quantum turnarounds. Interestingly, we find that very extreme energy densities can also occur for the holonomy quantization, breaching the maximum allowed density in the spatially flat loop quantized model. However, the expansion scalar in all these cases is bounded by a universal value.

On the nonlocality of the Coulomb gauge external field problem

The apparent nonlocality of the Coulomb gauge external field problem in electrodynamics is illustrated with an example in which nonlocality is especially striking. Explanation of this apparent nonlocal behaviour based on a purely local picture is given. A gauge invariant decomposition of the Lorentz-force into two terms with clear physical meanings is pointed out. Based on this decomposition derivation of the Aharonov–Bohm effect in terms of field strengths alone is given.

Non-linear uplift Ansätze for the internal metric and the four-form field-strength of maximal supergravity

The uplift of SO(8) gauged N=8 supergravity to 11-dimensional supergravity is well studied in the literature. It is given by consistent relations between the respective vector and scalar fields of both theories. For example, recent work provided non-linear uplift Ans\"atze for the scalar degrees of freedom on the internal manifold: the inverse metric and the three-form flux with mixed index structure. However, one always found the metric of the compactified manifold by inverting the inverse metric --- a task that was only possible in particular cases, e.g. for the G$_2$, SO(3)$\times$SO(3) or SU(3)$\times$U(1)$\times$U(1) invariant solutions of 11-dimensional supergravity. In this paper, I present a direct non-linear uplift Ansatz for the internal metric in terms of the four-dimensional scalars and the Killing forms on the compactified background manifold. Based on this formula, I also find new uplift Ans\"atze for the warp factor and the full three-form flux. Finally, I provide a direct non-linear uplift Ansatz for the internal four-form field-strength in terms of the metric, the flux as well as the four-dimensional scalars and background Killing forms. This new formula does not require to calculate the derivative of the flux. My results may be generalized to other compactifications, e.g. the reduction from type IIB supergravity to five dimensions.

Consistent 4-form fluxes for maximal supergravity

We derive new ansatze for the 4-form field strength of D = 11 supergravity corresponding to uplifts of four-dimensional maximal gauged supergravity. In particular, the ansatze directly yield the components of the 4-form field strength in terms of the scalars and vectors of the four-dimensional maximal gauged supergravity—in this way they provide an explicit uplift of all four-dimensional consistent truncations of D = 11 supergravity. The new ansatze provide a substantially simpler method for uplifting d = 4 flows compared to the previously available method using the 3-form and 6-form potential ansatze. The ansatz for the Freund-Rubin term allows us to conjecture a 'master formula' for the latter in terms of the scalar potential of d = 4 gauged supergravity and its first derivative. We also resolve a long-standing puzzle concerning the antisymmetry of the flux obtained from uplift ansatze.

Perpendicular-bias-field control of coupled vortex oscillations in nanodot networks

We studied, by combined micromagnetic numerical simulations and analytical derivations, coupled-vortex dynamics in one-dimensional (1D) arrays composed of two or more dipolar-coupled-vortex-state disks under perpendicular bias fields. We derived analytical expressions that could provide physical insights into the observed dynamic behaviors. The effects of perpendicular bias fields on the interaction strengths between the coupled-vortex oscillators and their characteristic band structures were examined and explained in terms of field strength and direction. Those effects showed that the normal modes and dispersion relations of collective vortex gyration, and the signal-transfer rate, can be tailored according to the derived explicit forms. The band width and gap of 1D coupled-vortex oscillator magnonic crystals, for example, are essential to the control of gyration-signal transfer in vortex-state dot networks. All of the analytical calculation results showed quantitatively good agreement with the micromagnetic simulation results, indicating that the perpendicular-bias-field dependence of coupled-vortex gyrations can be expressed simply as a function of the dynamic parameters under the zero field as well as the field strength and direction. This work provides not only a fundamental understanding of the effects of perpendicular bias fields on coupled-vortex oscillators but also an efficient practical means of dynamically manipulating collective vortex gyrations.

Optimizing the internal electric field distribution of alternating current driven organic light-emitting devices for a reduced operating voltage

The influence of the thickness of the insulating layer and the intrinsic organic layer on the driving voltage of p-i-n based alternating current driven organic light-emitting devices (AC-OLEDs) is investigated. A three-capacitor model is employed to predict the basic behavior of the devices, and good agreement with the experimental values is found. The proposed charge regeneration mechanism based on Zener tunneling is studied in terms of field strength across the intrinsic organic layers. A remarkable consistency between the measured field strength at the onset point of light emission (3–3.1 MV/cm) and the theoretically predicted breakdown field strength of around 3 MV/cm is obtained. The latter value represents the field required for Zener tunneling in wide band gap organic materials according to Fowler-Nordheim theory. AC-OLEDs with optimized thickness of the insulating and intrinsic layers show a reduction in the driving voltage required to reach a luminance of 1000 cd/m2 of up to 23% (8.9 V) and a corresponding 20% increase in luminous efficacy.

Electromagnetic Fields from Dental Devices and their Effects on Human Health

Magnetic fields can cause human health problems. Low-frequency electromagnetic fields are sometimes induced by electric currents in metallic objects that are worn or used in or on the body, and are unlike the high-frequency electromagnetic fields that produce heat. In low-frequency magnetic fields, the strength of the induced electric current is believed to be more important than the magnetic field strength in terms of effects on the health of living bodies. Electrically powered dental devices, including personal devices such as electric toothbrushes and professional devices such as curing lights for light-cured dental resins, are widely used because of their convenience, but the electric circuits and motors that power them produce low-frequency electromagnetic waves. These magnetic fields induce electric currents in teeth and in metallic appliances that are set in the oral cavity. The effects of these induced currents on human health must therefore be considered. Investigations of this issue revealed that magnetic fields from dental devices promoted the corrosion of intraoral metallic appliances via the induced currents, and this is likely to cause metallic allergies. Almost all reports on the effects of magnetic field exposure, including this corrosion phenomenon, describe harmful effects on human health. However, there may be some effective uses of the magnetic fields generated by dental devices for human health promotion. Oral bacteria were found to corrode orthodontic stainless steel appliances, but magnetic field-induced currents in these appliances could provide remarkable protection effects against this microbially induced corrosion. In this review, we discuss the results and conclusions of these investigations especially about novel ways of harmful effects and effective use of magnetic fields from dental devices, and conclude that further detailed studies are required to clarify their detailed mechanisms and to develop countermeasures for protection from or effective use of these fields.

A new interpretation of the far-infrared – radio correlation and the expected breakdown at high redshift

(Abrigded) Observations of galaxies up to z 2 show a tight correlation between far-infrared and radio continuum emission. We explain the far-infrared - radio continuum correlation by relating star formation and magnetic field strength in terms of turbulent magnetic field amplification, where turbulence is injected by supernova explosions from massive stars. We calculate the expected amount of turbulence in galaxies based on their star formation rates, and infer the expected magnetic field strength due to turbulent dynamo amplification. We estimate the timescales for cosmic ray energy losses via synchrotron emission, inverse Compton scattering, ionization and bremsstrahlung emission, probing up to which redshift strong synchrotron emission can be maintained. We find that the correlation between star formation rate and magnetic field strength in the local Universe can be understood as a result of turbulent magnetic field amplification. If the typical gas density in the interstellar medium increases at high z, we expect an increase of the magnetic field strength and the radio emission, as indicated by current observations. Such an increase would imply a modification of the far-infrared - radio correlation. We expect a breakdown when inverse Compton losses start dominating over synchrotron emission. For a given star formation surface density, we calculate the redshift where the breakdown occurs, yielding z (Sigma_SFR/0.0045 M_solar kpc^{-2} yr^{-1})^{1/(6-alpha/2)}. In this relation, the parameter \alpha describes the evolution of the characteristic ISM density in galaxies as (1+z)^\alpha. Both the possible raise of the radio emission at high redshift and the final breakdown of the far-infrared -- radio correlation at a critical redshift will be probed by the Square Kilometre Array (SKA) and its pathfinders, while the typical ISM density in galaxies will be probed with ALMA.

Exact half-BPS flux solutions inMtheory withD(2,1;c′;0)2symmetry: Local solutions

We construct local solutions to 11-dimensional supergravity (or M-theory), which are invariant under the superalgebra $D(2, 1; c'; 0)\oplus D(2, 1; c'; 0)$ for all values of the parameter $c'$. The BPS constraints are reduced to a single linear PDE on a complex function $G$. The PDE was solved in 0806.0605 modulo application of boundary and regularity conditions. The physical fields of the solutions are determined by $c'$, a harmonic function $h$, and the complex function $G$. $ h$ and $G$ are both functions on a 2-dimensional compact Riemannian manifold. The harmonic function $ h$ is freely chosen. We obtain the expressions for the metric and the field strength in terms of $G$, $h$, and $c'$ and show that these are indeed valid solutions of the Einstein, Maxwell, and Bianchi equations. Finally we give a construction of one parameter deformations of $AdS_7 \times S^4$ and $AdS_4 \times S^7$ as a function of $c'$.

Loop variables and gauge invariant exact renormalization group equations for (open) string theory

An exact renormalization group equation is written down for the world sheet theory describing the bosonic open string in general backgrounds. Loop variable techniques are used to make the equation gauge invariant. This is worked out explicitly up to level 3. The equation is quadratic in the fields and can be viewed as a proposal for a string field theory equation. As in the earlier loop variable approach, the theory has one extra space dimension and mass is obtained by dimensional reduction. Being based on the sigma model RG, it is background independent. It is intriguing that in contrast to BRST string field theory, the gauge transformations are not modified by the interactions up to the level calculated. The interactions can be written in terms of gauge invariant field strengths for the massive higher spin fields and the non-zero mass is essential for this. This is reminiscent of Abelian Born–Infeld action (along with derivative corrections) for the massless vector field, which is also written in terms of the field strength.

Overhauser DNP with15N labelled Frémy's salt at 0.35 Tesla

The effectiveness of dynamic nuclear polarization (DNP) as a tool to enhance the sensitivity of liquid state NMR critically depends on the choice of the optimal polarizer molecule. In this study the performance of (15)N labelled Frémy's salt as a polarizing agent in Overhauser DNP is investigated in detail at X-band (0.35 T, 9.7 GHz EPR, 15 MHz (1)H NMR) and compared to that of TEMPONE-D,(15)N employed in previous studies. Both radicals provide similar maximum enhancements of the solvent water protons under similar conditions but a different saturation behaviour. The factors determining the enhancement and effective saturation were measured independently by EPR, ELDOR and NMRD and are shown to fulfil the Overhauser equation. In particular, following the theory of EPR saturation we provide analytical solutions for the dependence of the enhancement on the microwave field strength in terms of saturation transfer between two coupled hyperfine lines undergoing spin exchange. The negative charge of the radical in Frémy's salt solutions can explain the peculiar properties of this polarizing agent and indicates different suitable application areas for the two types of nitroxide radicals.