The electric dipole response of even-even 154-164Dy isotopes

The excitation of pygmy dipole resonance (PDR) and giant dipole resonance (GDR) in even-even 154-164Dy isotopes is examined through quasiparticle random-phase approximation (QRPA) with the effective interactions that restores the broken translational and Galilean invariances. In each isotope, an electric response emerges by showing ample distribution at energies below and above 10 MeV. We, therefore, study the transition cross sections and probabilities, photon strength functions, transition strengths, isospin character, and collectivity of the predicted E1 responses.

Ions, adsorption and electric response of a ferrofluid cell

We show that the electric response of a cell in the shape of a slab containing a ferrofluids (magnetic particles in kerosene) can be interpreted by means of a model...

Multiferroic Coupling of Ferromagnetic and Ferroelectric Particles through Elastic Polymers

Multiferroics are materials that electrically polarize when subjected to a magnetic field and magnetize under the action of an electric field. In composites, the multiferroic effect is achieved by mixing of ferromagnetic (FM) and ferroelectric (FE) particles. The FM particles are prone to magnetostriction (field-induced deformation), whereas the FE particles display piezoelectricity (electrically polarize under mechanical stress). In solid composites, where the FM and FE grains are in tight contact, the combination of these effects directly leads to multiferroic behavior. In the present work, we considered the FM/FE composites with soft polymer bases, where the particles of alternative kinds are remote from one another. In these systems, the multiferroic coupling is different and more complicated in comparison with the solid ones as it is essentially mediated by an electromagnetically neutral matrix. When either of the fields, magnetic or electric, acts on the ‘akin’ particles (FM or FE) it causes their displacement and by that perturbs the particle elastic environments. The induced mechanical stresses spread over the matrix and inevitably affect the particles of an alternative kind. Therefore, magnetization causes an electric response (due to the piezoeffect in FE) whereas electric polarization might entail a magnetic response (due to the magnetostriction effect in FM). A numerical model accounting for the multiferroic behavior of a polymer composite of the above-described type is proposed and confirmed experimentally on a polymer-based dispersion of iron and lead zirconate micron-size particles.

Recent advances in bianisotropic boundary conditions: theory, capabilities, realizations, and applications

In recent years, new functionality and unprecedented wavefront control has been enabled by the introduction of bianisotropic metasurfaces. A bianisotropic metasurface is characterized by an electric response, a magnetic response, and an electro-magnetic/magneto-electric response. In general, these metasurfaces consists of an array of metallic or dielectric particles located within a subwavelength thick host medium, and are approximated and modeled as infinitely-thin, idealized sheet boundaries defined along a surface. An appropriate sheet boundary condition which effectively models the tangential field discontinuity due to the array of magnetoelectric inclusions is the Generalized Sheet Transition Condition or GSTC. Several forms of the GSTC appear in literature. Here, we present each interpretation and show how they are related. Synthesis approaches unique to each form are overviewed. By utilizing the GSTC in metasurface design, new possibilities emerge which are not possible with conventional design techniques incorporating only electric or only magnetic responses. Since the metasurfaces are designed using bianisotropic boundary conditions, they must be realized using particles which contain magnetoelectric responses. This review article discusses the design of metasurfaces using the GSTC, and the bianisotropic particles used to realize GSTC’s. Further, it discusses new and recent applications that have emerged due to bianisotropy, and future prospects in metasurface design using bianisotropic boundary conditions. The intent is to provide a comprehensive overview of metasurface design involving bianisotropy and for this review article to serve as a starting point for engineers and scientist that wish to introduce bianisotropy into metasurface design.

Zebrafish Larvae's Response to Electricity is Mediated by Dopaminergic Agonists and Antagonists

The signaling molecular mechanisms in zebrafish response to electricity are unknown, so here we asked if changes to dopaminergic signaling pathways can affect their electrically-evoked locomotion. To answer this question, the effects of multiple selective and non-selective dopamine compounds on the electric response of zebrafish larvae is investigated. A microfluidic device with enhanced control of experimentation with multiple larvae is used, which features a novel design to immobilize four zebrafish larvae in parallel and expose them to electric current that induces tail locomotion. In 6 days post-fertilization zebrafish larvae, the electric induced locomotor response is quantified in terms of the tail movement duration and beating frequency to discern the effect of non-lethal concentrations of dopaminergic agonists (apomorphine, SKF-81297, and quinpirole), and antagonists (butaclamol, SCH-23390, and haloperidol). All dopamine antagonists decrease locomotor activity, while dopamine agonists do not induce similar behaviours in larvae. The D2- like selective dopamine agonist quinpirole enhances movement. However, exposure to non-selective and D1-selective dopamine agonists apomorphine and SKF-81297 cause no significant change in the electric response. Exposing larvae that were pre-treated with butaclamol and haloperidol to apomorphine and quinpirole, respectively, restores electric locomotion. The results demonstrate a correlation between electric response and the dopamine signalling pathway. We propose that the electrofluidic assay has profound application potential as a chemical screening method when investigating biological pathways, behaviors, and brain disorders.

Pressure Retarded Osmosis Power Units Modelling for Power Flow Analysis of Electric Distribution Networks

Pressure retarded osmosis (PRO) power units, which produce electrical energy from salinity gradient sources located at coastlines, are a technology still in the process of maturation; however, there is an expectation that this technology will need to be integrated into electrical distribution networks. Such integration will drive changes in the electric response of the distribution systems which may lead to harmful operating conditions. Power flow analysis is a tool used to reveal the steady-state operating condition of distribution systems and which could be extended to study and address the integration of PRO power units. To the best of the authors’ knowledge, such extension of power flow analysis has not yet been addressed in the literature. Accordingly, this paper comprehensively provides a model to evaluate the electric current and complex power produced by PRO power units. This model is directly embedded in the forward-backward sweep (FBS) method, extending the power flow analysis of electric distribution systems in this way so as to consider the integration of PRO power units. The resulting approach permits revealing of the steady-state operating response of distribution systems and the effects that may be driven by the integration of PRO power units, as corroborated through numerical results on a 14-node test distribution system.

Zebrafish Larva’s Response and Habituation to Electric Signal: Effects of Voltage, Current and Pulsation Studied in a Microfluidic Device

We previously showed that electric current can cause zebrafish larvae to move towards the anode pole along a microchannel. For a semi-mobile larva, we observed that zebrafish response to electricity depended on the current magnitude. The effects of electric signal direction, voltage magnitude and habituation to repeated exposures to electric pulses were not characterized. Here, this knowledge gap was addressed by exploiting these parameters in a microfluidic device with a head-trap to immobilize a zebrafish larva and a downstream chamber for tail movement and phenotypic characterization of response duration (RD) and tail beat frequency (TBF). We first assessed larvae’s response to electric current direction (at 3µA) and voltage magnitude. Changing the current direction significantly altered the RD and TBF with long and low-frequency responses seen when the anode was positioned at larvae’s tail. The electric voltage drop across the fish body had a significant effect on larvae’s locomotion with long RD and low TBF observed at 5.6V in the range of 1.3-9V. We also demonstrated that the zebrafish locomotor response to repeated 3µA current pulses diminished with dependency on the interstimulus interval. However, the diminished response was fully recovered after a 5-min resting period or introduction of a novel light stimulus (i.e. habituation-dishabituation strategy). Therefore, electric response suppression in zebrafish was attributed to the habituation as a form of non-associative learning. Our microfluidic platform has broad application potential in behavioral neuroscience to study cognitive phenotypes, fundamental studies on the biological roots of electric response, and pharmacological screening.

Recent Advances and Challenges in the Development of Radiofrequency HTS Coil for MRI

Radiofrequency (RF) coils fashioned from high-temperature superconductor (HTS) have the potential to increase the sensitivity of the magnetic resonance imaging (MRI) experiment by more than a dozen times compared to conventional copper coils. Progress, however, has been slow due to a series of technological hurdles. In this article, we present the developments that recently led to new perspectives for HTS coil in MRI, and challenges that still need to be solved. First, we recall the motivations for the implementations of HTS coils in MRI by presenting the limits of cooled copper coil technology, such as the anomalous skin effect limiting the decrease of the electric resistance of normal conductors at low temperature. Then, we address the progress made in the development of MRI compatible cryostats. New commercially available low-noise pulsed-tube cryocoolers and new materials removed the need for liquid nitrogen-based systems, allowing the design of cryogen-free and more user-friendly cryostats. Another recent advance was the understanding of how to mitigate the imaging artifacts induced by HTS diamagnetism through field cooling or temperature control of the HTS coil. Furthermore, artifacts can also originate from the RF field coupling between the transmission coil and the HTS reception coil. Here, we present the results of an experiment implementing a decoupling strategy exploiting nonlinearities in the electric response of HTS materials. Finally, we discuss the potential applications of HTS coils in bio-imaging and its prospects for further improvements. These include making the technology more user-friendly, implementing the HTS coils as coil arrays, and proposing solutions for the ongoing issue of decoupling. HTS coil still faces several challenges ahead, but the significant increase in sensitivity it offers lends it the prospect of being ultimately disruptive.

Investigation of the Phase Transitions and Magneto-Electric Response in the 0.9(PbFe0.5Nb0.5)O3-0.1Co0.6Zn0.4Fe1.7Mn0.3O4 Particulate Composite

Multiferroic composites with enhanced magneto-electric coefficient are suitable candidates for various multifunctional devices. Here, we chose a particulate composite, which is the combination of multiferroic (PbFe0.5Nb0.5O3, PFN) as matrix and magnetostrictive (Co0.6Zn0.4Fe1.7Mn0.3O4, CZFMO) material as the dispersive phase. The X-ray diffraction analysis confirmed the formation of the composite having both perovskite PFN and magnetostrictive CZFMO phases. The scanning electron micrograph (SEM) showed dispersion of the CZFMO phase in the matrix of the PFN phase. The temperature-dependent magnetization curves suggested the transition arising due to PFN and CZFMO phase. The temperature-dependent dielectric study revealed a second-order ferroelectric to the paraelectric phase transition of the PFN phase in the composite with a small change in the transition temperature as compared to pure PFN. The magnetocapacitance (MC%) and magnetoimpedance (MI%) values (obtained from the magneto-dielectric study at room temperature (RT)) at 10 kHz were found to be 0.18% and 0.17% respectively. The intrinsic magneto-electric coupling value for this composite was calculated to be 0.14 mVcm−1Oe−1, which is comparable to other typical multiferroic composites in bulk form. The composite PFN-CZFMO exhibited a converse magneto-electric effect with a change in remanent magnetization value of −58.34% after electrical poling of the material. The obtained outcomes from the present study may be utilized in the understanding and development of new technologies of this composite for spintronics applications.