Presence Of Weak Electric Field Research Articles

Bumblebee hair motion in electric fields

Bees have been observed to detect and learn the presence of weak electric fields in various behavioural experiments in the lab. The electro-sensitivity of bumblebees has also been suggested to be important for pollination. However, the structure and function of electro-sensory organs are yet to be described. Bees, like other arthropods, are known to have evolved various mechanoreceptors. Antennae and hairs have mechanosensory functions and have been shown to respond to weak electric fields. Current proposals posit that hairs and antennae can act as electromechanical sensors. To investigate this hypothesis, the mechanical response of bumblebee hairs stimulated by an electric field was measured using microscanning laser Doppler vibrometry. Hair vibration velocity is shown to be proportional to charge triboelectrically deposited on the bee and the effect of polarisation charge is seen to be negligible. Hair motion due to acoustic stimuli is also measured and compared to hair electromechanical response. Preliminary results show that the electro-sensitivity of charged bee hairs is comparable to hair sensitivity to acoustic stimuli.

Electrical conductivity of a methane–air burning plasma under the action of weak electric fields

This paper focuses on the calculation of the electrical conductivity of a methane–air flame in the presence of weak electric fields, solving the Boltzmann equation for free electrons self-consistently coupled with chemical kinetics. The chemical model GRI-Mech 3.0 has been completed with chemi-ionization reactions to model ionization in the absence of fields, and a database of cross sections for electron-impact-induced processes to account for reactions and transitions activated in the flame during discharge. The dependence of plasma properties on the frequency of an oscillating field has been studied under different pressure and gas temperature conditions. Fitting expressions of the electrical conductivity as a function of gas temperature and methane consumption are provided for different operational conditions in the Ansaldo Energia burner.

Hot-electron effect in spin relaxation of electrically injected electrons in intrinsic Germanium

The hot-electron effect in the spin relaxation of electrically injected electrons in intrinsic germanium is investigated by the kinetic spin Bloch equations both analytically and numerically. It is shown that in the weak-electric-field regime with E ≲ 0.5 kV cm−1, our calculations have reasonable agreement with the recent transport experiment in the hot-electron spin-injection configuration (2013 Phys. Rev. Lett. 111 257204). We reveal that the spin relaxation is significantly enhanced at low temperature in the presence of weak electric field E ≲ 50 V cm−1, which originates from the obvious center-of-mass drift effect due to the weak electron–phonon interaction, whereas the hot-electron effect is demonstrated to be less important. This can explain the discrepancy between the experimental observation and the previous theoretical calculation (2012 Phys. Rev. B 86 085202), which deviates from the experimental results by about two orders of magnitude at low temperature. It is further shown that in the strong-electric-field regime with 0.5 ≲ E ≲ 2 kV cm−1, the spin relaxation is enhanced due to the hot-electron effect, whereas the drift effect is demonstrated to be marginal. Finally, we find that when 1.4 ≲ E ≲ 2 kV cm−1 which lies in the strong-electric-field regime, a small fraction of electrons (≲5%) can be driven from the L to Γ valley, and the spin relaxation rates are the same for the Γ and L valleys in the intrinsic sample without impurity. With the negligible influence of the spin dynamics in the Γ valley to the whole system, the spin dynamics in the L valley can be measured from the Γ valley by the standard direct optical transition method.

Electric-field-enhanced nutrient consumption in dielectric biomaterials that contain anchorage-dependent cells

This research contribution addresses electric-field stimulation of intra-tissue mass transfer and cell proliferation in viscoelastic biomaterials. The unsteady state reaction–diffusion equation is solved according to the von Kármán–Pohlhausen integral method of boundary layer analysis when nutrient consumption and tissue regeneration occur in response to harmonic electric potential differences across a parallel-plate capacitor in a dielectric-sandwich configuration. The partial differential mass balance with diffusion and electro-kinetic consumption contains the Damköhler (Λ 2) and Deborah (De) numbers. Zero-field and electric-field-sensitive Damköhler numbers affect nutrient boundary layer growth. Diagonal elements of the 2nd-rank diffusion tensor are enhanced in the presence of weak electric fields, in agreement with the formalism of equilibrium and nonequilibrium thermodynamics. Induced dipole polarization density within viscoelastic biomaterials is calculated via the real and imaginary components of the complex dielectric constant, according to the Debye equation, to quantify electro-kinetic stimulation. Rates of nutrient consumption under zero-field conditions are described by third-order kinetics that include local mass densities of nutrients, oxygen, and attached cells. Thinner nutrient boundary layers are stabilized at shorter dimensionless diffusion times when the zero-field intra-tissue Damköhler number increases above its initial-condition-sensitive critical value [i.e., {Λ 2 zero-field} critical ≥ 53, see Eq. (23)], such that the biomaterial core is starved of essential ingredients required for successful proliferation. When tissue regeneration occurs above the critical electric-field-sensitive intra-tissue Damköhler number, the electro-kinetic contribution to nutrient consumption cannot be neglected. The critical electric-field-sensitive intra-tissue Damköhler number is proportional to the Deborah number.

A mathematical model in three-dimensional piezoelectric continuum to predict non-linear responses of piezoceramic materials

It has been experimentally observed that the piezoceramic materials exhibit different types of non-linearities under different combinations of electrical and mechanical fields. When excited near resonance in the presence of weak electric fields, they exhibit typical non-linearities similar to a Duffing oscillator such as jump phenomena and the presence of superharmonics in the response spectra. In this work, these non-linearities have been modelled for a generalized three-dimensional piezoelectric continuum using higher-order quadratic and cubic terms in the electric enthalpy density function and the virtual work. The identification of the parameters of the model requires a closed form solution for non-linear response of a simplified geometry. A simple proportional damping formulation has been used in the model. Experiments have been conducted on rectangular and cylindrical geometries of piezoceramic PIC 181 at different magnitudes of applied electric fields and results have been compared with those of simulation.

Ionization distances of Rydberg atoms approaching solid surfaces in the presence of weak electric fields

The ionization distances ${R}_{c}^{I}$ of slow hydrogenlike Rydberg atoms approaching solid surfaces in the presence of a weak external electric field are calculated. The ionization is treated as resonant electron tunneling in the very vicinity of the top of the potential barrier, created between the ionic core and polarized solid. We obtain both the complex energies and the ionization distances by solving the energy eigenvalue problem under the outgoing wave boundary condition towards the solid. The eigenvalue problem is studied in parabolic coordinates within the framework of an etalon equation method adapted to include the confluence of turning points. It is demonstrated that in a critical region $R\ensuremath{\approx}{R}_{c}^{I}⪢1\phantom{\rule{0.3em}{0ex}}\mathrm{a}.\mathrm{u}.$ of ion-surface distances $R$, parabolic quantum numbers ${n}_{1}$, ${n}_{2}$, and $m$ can serve as approximate, but ``sufficiently good'' quantum numbers, at least for lower ${n}_{1}$ values. The method offers asymptotically exact analytical expressions for the ionization rates and energies, which follow the theoretical predictions of the complex scaling method (CSM). It is also found that the resulting ionization distances ${R}_{c}^{I}$ are in very good agreement with the results of CSM. The implications of using obtained results in analyzing the recent xenon experimental data for ${R}_{c}^{I}$ are briefly discussed.

Nonlinear behaviour of piezoceramics under weak electric fields: Part-I: 3-D finite element formulation

Piezoceramic materials exhibit different types of nonlinearities under different combinations of electric and mechanical fields. When excited near resonance in the presence of weak electric fields, they exhibit typical nonlinearities similar to a Duffing oscillator such as jump phenomena and presence of superharmonics in the response spectra. In order to model such nonlinearities, a nonlinear electric enthalpy density function (using quadratic and cubic terms) valid for a general 3-D piezoelectric continuum has been proposed in this work. Linear (i.e. proportional) and nonlinear damping models have also been proposed. The coupled nonlinear finite element equations have been derived using variational formulation. The classical linearization technique has been used to derive the linearized stiffness and damping matrices which helps in assembling the nonlinear matrices and solution of resulting nonlinear equation. The general 3-D finite element formulation is discussed in this paper. In a companion paper by Samal et al., numerical results on various typical examples are shown to match very well with the experimental observations.

Nonlinear behaviour of piezoceramics under weak electric fields. Part-II: Numerical results and validation with experiments

When excited near resonance in the presence of weak electric fields, piezoceramic materials exhibit typical nonlinearities similar to a Duffing oscillator such as jump phenomena and presence of superharmonics in the response spectra. In an accompanying paper, a generalized nonlinear 3D finite element formulation has been developed incorporating quadratic and cubic terms in the electric enthalpy density function and the virtual work done by damping forces. In this paper, the formulation has been validated by conducting experiments on test pieces of various geometries and of three different materials (in all, four case studies). Both proportional damping and nonlinear damping formulations have been used to predict the frequency response of these systems. Newmark- β method has been used to obtain the dynamic response of the systems using FE analysis. It is demonstrated that the nonlinear finite element model is able to predict the responses of the various test cases studied and the results match very well with those of experimental observations.

Perception of local DC and AC electric fields in humans

The goal of this study was to address some of the factors that contribute to the human ability to detect the presence of weak electric fields generated by direct current (DC) and alternating current (AC) sources. An exposure chamber allowed us to expose a limited surface of the body (forearm and hand) to DC fields of up to 65 kV/m and AC fields up to a maximum of 35 kV/m (frequency 60 Hz). Perception was examined using a staircase procedure and a rating procedure derived from signal detection theory. Sixteen subjects participated in the experiments, and none detected the local DC fields. In contrast, 9/16 subjects were sensitive to local AC electric fields, although detection thresholds (index of sensitivity, d' = 1.0) were widely variable between subjects. When regional exposure was limited to the dorsal forearm, performance was similar to that seen when the forearm and hand were exposed. In contrast, subjects did not reliably detect the AC electric fields when exposure was limited to the hand (either hairy or glabrous skin), although a minority of subjects (3/9) showed some evidence of detecting fields presented to the glabrous palm. Subjects were unable to detect AC electric fields when the hair was removed from the forearm and hand, suggesting that the evoked sensation is mainly dependent on movement of hair located in the exposed region.

Electron temperature in a decaying molecular nitrogen plasma in the presence of weak electric fields

The electron energy distribution function in an afterglow molecular nitrogen plasma is studied both experimentally and theoretically under the conditions of weak electric fields such that the electron gas is heated by superelastic collisions of electrons with vibrationally excited molecules. Based on the mean electron energy balance, it is established that, depending on the degree of plasma ionization and the vibrational temperature of nitrogen molecules, an afterglow plasma may evolve into two states, differing in electron temperature. This kind of bistability is found to stem from the difference in the main mechanisms for electron energy losses in the two stable states. The prediction that the shape of the electron energy distribution function should change in a jumplike manner when a weak electric field is imposed has been confirmed experimentally.

Theory and applications of internal photoemission in the MOS system at low electric fields

A new theory is presented of the photoelectric phenomena, which take place in UV illuminated MOS structures, in the presence of weak electric fields (|E|<104V/cm) in the dielectric. The problem is formulated in appropriate equations and solved separately for the cases of zero (J=0) and nonzero (J≠0) photocurrents. The solutions obtained are shown to remain in excellent agreement with experiment, which supports the validity of the theory. This theory finds applications in developing new, very sensitive, photoelectric measurement methods of the MOS system parameters. Two of such methods are shortly presented. The first is the measurement method of the φMS factor of the MOS system, which has already been fully verified experimentally and has been shown to be the most accurate of the existing methods of this parameter determination. The second is the method to determine trapping properties of the dielectric in the MOS system, which is currently being optimized and verified experimentally.

Sensory receptors in monotremes.

This is a summary of the current knowledge of sensory receptors in skin of the bill of the platypus, Ornithorhynchus anatinus, and the snout of the echidna, Tachyglossus aculeatus. Brief mention is also made of the third living member of the monotremes, the long-nosed echidna, Zaglossus bruijnii. The monotremes are the only group of mammals known to have evolved electroreception. The structures in the skin responsible for the electric sense have been identified as sensory mucous glands with an expanded epidermal portion that is innervated by large-diameter nerve fibres. Afferent recordings have shown that in both platypuses and echidnas the receptors excited by cathodal (negative) pulses and inhibited by anodal (positive) pulses. Estimates give a total of 40,000 mucous sensory glands in the upper and lower bill of the platypus, whereas there are only about 100 in the tip of the echidna snout. Recording of electroreceptor-evoked activity from the brain of the platypus have shown that the largest area dedicated to somatosensory input from the bill, S1, shows alternating rows of mechanosensory and bimodal neurons. The bimodal neurons respond to both electrosensory and mechanical inputs. In skin of the platypus bill and echidna snout, apart from the electroreceptors, there are structures called push rods, which consist of a column of compacted cells that is able to move relatively independently of adjacent regions of skin. At the base of the column are Merkel cell complexes, known to be type I slowly adapting mechanoreceptors, and lamellated corpuscles, probably vibration receptors. It has been speculated that the platypus uses its electric sense to detect the electromyographic activity from moving prey in the water and for obstacle avoidance. Mechanoreceptors signal contact with the prey. For the echidna, a role for the electrosensory system has not yet been established during normal foraging behaviour, although it has been shown that it is able to detect the presence of weak electric fields in water. Perhaps the electric sense is used to detect moving prey in moist soil.

Dielectronic recombination of light Be-like and B-like ions

Dielectronic recombination cross sections from the ground and metastable states of the Be-like ions C2+, O4+ and F5+, and the B-like ions O3+ and F4+, have been calculated and compared with experimental results obtained by a merged-beams technique. The comparison of theory and experiment is complicated by the presence of weak electric fields in the interaction region. However, the authors qualitatively explain the main features of their experimental results. In particular, for Be-like ions they find evidence of a large contribution from the initial 2s2p 3P metastable state recombining into an Auger metastable final state.

Decrease of electron temperature by electric fields

It is shown by extending the calculations of Stratton of integrals in the optical scattering equations to include higher order terms that the presence of weak electric fields in semiconductors may decrease the electron temperature, T, below the lattice temperature, T0, although the total energy change, E-32kT0, is always positive.