Range Of Electric Field Strengths Research Articles

Hybridization of Trichoderma reesei protoplasts by electrofusion

Trichoderma reesei strains belong to the group of industrially important microorganisms because of their ability to produce cellulase enzymes. A method for strain improvement is protoplast fusion. We tested the potential of electrofusion in protoplast hybridization in the case of two auxotrophic strains (ade − lys − and ade − leu −). After dielectrophoretic cell collection (500 V/cm, 1 MHz) we used rectangular fusion pulses in a range of electric field strengths E = 1–4.5 kV/cm and pulse durations τ = 25–120 μs (number of pulses N = 1–5). An optimal yield of hybrids able to form colonies on minimal/ade-medium was found at E = 4.1 kV/cm, τ = 75 μs, and N = 5.28% of the fusants selected statistically were stable and most of them showed a changed behaviour in catabolite repression. These results indicate new possibilities for strain improvement in T. reesei.

Hybridization of Trichoderma reesei protoplasts by electrofusion

Trichoderma reesei strains belong to the group of industrially important microorganisms because of their ability to produce cellulase enzymes. A method for strain improvement is protoplast fusion. We tested the potential of electrofusion in protoplast hybridization in the case of two auxotrophic strains (ade −lys − and ade −leu −). After dielectrophoretic cell collection (500 V/cm, 1 MHz) we used rectangular fusion pulses in a range of electric field strengths E = 1–4.5 kV/cm and pulse durations τ = 25–120 μs (number of pulses N = 1–5). An optimal yield of hybrids able to form colonies on minimal/ade-medium was found at E = 4.1 kV/cm, τ = 75 μs, and N = 5. 28% of the fusants selected statistically were stable and most of them showed a changed behaviour in catabolite repression. These results indicate new possibilities for strain improvement in T. reesei.

Efficient optical excitation of the highest energy level of the N=17 Stark manifold in barium

The authors report on two-photon laser experiments on the n=17 Stark manifold of Ba in an electric field varying from 0 to 1170 V cm-1. The observed wavelengths and peak intensities in the manifold are compared with the predictions of the diagonalisation method developed by Zimmerman et al. (1978-1979). Efficient excitation of the highest energy level in the Stark manifold is shown to take place inside a narrow range of electric field strength. This feature turns out to be favourable for future preparation of circular atoms ( mod m mod =l=n-1).

The Electric Birefringence and Dichroism of a Nonlinear Optical Compound, 4-[2-[4-(Dimethylamino)pheny]ethenyl]-1-ethylpyridinium Iodide, in the Presence of Poly(p-styrenesulfonate) and Poly(l-α-glutamate) in Solutions

Abstract The pulsed electric birefringence at 633 nm and dichroism at 462 nm of the title cationic compound (DAES) were measured at 20 °C over a wide electric field strength range (0.1–24 kV cm−1) in the presence of poly(p-styrenesulfonate) (NaPSS) and poly(l-α-glutamate) (PGA) in aqueous solutions at various mixing ratios (P/D) of the polymer to the ligand. The steady-state electric birefringence δ of NaPSS–DAES complexes was positive, while that of NaPSS was negative. The optical anisotropy factor of bound DAES was responsible for the sign reversal. The reduced electric dichroism of NaPSS–DAES at a P/D of 1.9 was +0.38 at infinitely high fields. A value of ±50° was found for the average angle between the orientation axis of the complex and the direction of the optical transition moment at 462 nm of bound DEAS chromophores. No appreciable permanent dipole moment was present in any of the NaPSS–DAES systems. The field orientation was due mostly to counterion-induced moments. The rotational relaxation time was determined from the decay signals. For PAG–DAES and PGA at pH 6.4 and 4.1, the sign of δ was always positive, the magnitude differing from each other by only 10–20%.

Acetylcholine receptors and concanavalin A-binding sites on cultured Xenopus muscle cells: electrophoresis, diffusion, and aggregation.

Using digitally analyzed fluorescence videomicroscopy, we have examined the behavior of acetylcholine receptors and concanavalin A binding sites in response to externally applied electric fields. The distributions of these molecules on cultured Xenopus myoballs were used to test a simple model which assumes that electrophoresis and diffusion are the only important processes involved. The model describes the distribution of concanavalin A sites quite well over a fourfold range of electric field strengths; the results suggest an average diffusion constant of approximately 2.3 X 10(-9) cm2/s. At higher electric field strengths, the asymmetry seen is substantially less than that predicted by the model. Acetylcholine receptors subjected to electric fields show distributions substantially different from those predicted on the basis of simple electrophoresis and diffusion, and evidence a marked tendency to aggregate. Our results suggest that this aggregation is due to lateral migration of surface acetylcholine receptors, and is dependent on surface interactions, rather than the rearrangement of microfilaments or microtubules. The data are consistent with a diffusion-trap mechanism of receptor aggregation, and suggest that the event triggering receptor localization is a local increase in the concentration of acetylcholine receptors, or the electrophoretic concentration of some other molecular species. These observations suggest that, whatever mechanism(s) trigger initial clustering events in vivo, the accumulation of acetylcholine receptors can be substantially enhanced by passive, diffusion-mediated aggregation.

Reduction of the nocturnal rise in pineal melatonin levels in rats exposed to 60-Hz electric fields in utero and for 23 days after birth

Rats exposed to 60-Hz electric fields of either 10, 65, or 130 kV/m from conception to 23 days of age exhibited reduced peak nighttime pineal melatonin contents compared to unexposed controls. As a group, the exposed rats also exhibited a phase delay, estimated at approximately 1.4 hours, in the occurrence of the nocturnal melatonin peak. No clear dose-response relationship was noticed over the range of electric field strengths used as treatments in these experiments. These are the first studies concerned with the effects of electric field exposure on the pineal melatonin rhythm in immature rats. The findings are generally consistent with those obtained using adult rats, where electric field exposure has been shown to abolish the nighttime rhythm in pineal melatonin concentrations.

Field ion energy deficit calculations for liquid metal ion sources

Ionisation distributions of field-ionised ions from liquid metal ion sources are calculated. Various shapes for the emitter region, a range of currents and a range of electric field strengths at the liquid surface are considered. Their effects on the energy deficit distribution of the ions is presented through a numerical calculation for gold and gallium.

A model study of field-dependent dynamical screening due to mobile electrons in submicron semiconductor devices

A previously obtained generalised field-dependent screening function involving one-electron Wigner distributions and spectral functions is studied under various model approximations. The field dependence of the screening arises from the action of a (constant) electric field within duration of a collision process (estimated from the uncertainty relations) and has the effect of reducing the screening efficiency. This field-induced descreening effect is studied analytically and numerically for a range of electric field strengths and electron temperatures and densities in both three- and two-dimensional non-degenerate electron assemblies. The model assumed allows the influences of displaced Maxwellian distribution functions and finite electron quasiparticle lifetimes to be considered.

Temperature dependent electron velocity-field characteristics for In0.53Ga0.47AS at high electric fields

The static electron velocity-field characteristics for n-In0.53Gan0.47AS have been measured at temperatures from 95 K to 300 K over a range of electric field strengths from about 10 kV/cm to beyond 100 kV/cm. The velocity decreases monotonically with increasing electric field at all temperatures over the range of field strengths investigated. The electron velocity-field curves for In0.53Ga0.47As exhibit a larger peak-to-valley ratio, lower high-field velocity, and a smaller high-field temperature dependence than those for GaAs measured using the same experimental technique.

Electric Linear Dichroism Study of Sodium Poly(p-styrenesulfonate) and Its 9-Aminoacridinium Complex in Aqueous Solutions

Abstract Electric linear dichroism (ELD) of sodium poly(p-styrenesulfonate) (NaPSS) and its 9-aminoacridinium (AA) complex at a mixing ratio of polymer residue-to-dye of 6.14 was studied in aqueous solutions at 20 °C. ELD signals were measured in the electric field strength range 0—ca. 19 kV/cm at the absorption peak wavelengths; they showed a saturating trend at extremely high fields. The average angles between the orientation axis of NaPSS and the transition moments of chromophores were estimated to be 60° at 224.5 nm and 57° at 262 nm for the side chain phenyl group and 50° at 404 nm for the bound AA by using theoretical orientation functions derived for mono- and polydisperse systems. The ELD spectra were measured at fixed field strengths; 275–215 nm for NaPSS and 440–282 nm for NaPSS–AA. The reduced dichroism of NaPSS remained nearly constant throughout the 262 nm band but steadily changed below 224 nm in the 224.5 nm band, indicating that another band exists in the far UV region. The ELD spectrum of the NaPSS–AA complex revealed that the two electronic 1La and 1Lb transition moments of the bound AA are tilted at different angles to the orientation axis of the NaPSS backbone.

Investigation of some characteristics of a liquid methane pulsed ionization chamber

The yield of free electrons from the tracks of electrons with an energy of E e = 1.06 MeV and protons of E p = 14.5 MeV has been measured in liquid methane. The electric field strength dependence of the attachment coefficient of electrons to O 2 molecules in liquid methane for E = 0.18–1.8 kV . cm −1 has been obtained. The electron drift velocities in liquid methane and mixtures (Ar + CH 4) with methane content of 1%, 5% and 10% in the range of electric field strengths of E = 0.3–2 kV . cm −1 have been measured. The liquid methane chamber was used to detect neutrons with an energy of 14.5 MeV.

Field and Frequency Effects in a Nematic Mixture of Negative and Positive Dielectric Anisotropy

Abstract The molecular alignment in the nematic liquid crystal mixture of p-ethoxy benzylidene p′-n-butyl aniline (EBBA) and p-ethoxy benzylidene p′-cyano aniline (EBCA) has been investigated by measuring the dielectric constant at 1 MHz. Detailed investigation has been carried out for a composition of 2.74%, of EBCA in EBBA for different electric and magnetic field strengths and at different frequencies of the applied electric field. Both parallel and perpendicular electric and magnetic field configurations have been employed. Temperature and frequency dependence of the dielectric anisotropy have been studied. Two interesting features have been observed. I) In the crossed field configuration complete molecular alignment could be observed by suitably changing the electric field strength. The range of electric field strength required to change the molecular ordering, is frequency dependent. This range shows a minimum in the neighbourhood of 2 kHz. 2) It has also been observed that in the parallel field con...

Collective interactions and electrical conductivity of plasma in strong electric fields

This work includes the analysis of experiments, made at the Physico-Technical Institute of the Academy of Sciences of the Ukrainian SSR, which investigated the anomalous electrical conductivity of plasma over a wide range of electric field strengths. The plasma conductivity at medium electric fields is shown to depend in a complex way on the electric field, the exact nature depending upon the type of magnetic trap. Streaming instabilities, primarily the ion sound instabilities, are the main physical mechanisms governing the anomaly of resistance. At high electric fields the electrical conductivity of plasma does not depend upon the value of electric field strength nor upon the plasma temperature, but is proportional to square root n. The dynamics of streaming instabilities in the discharge are studied, and their relative importance in the process of development of a gas discharge is clarified. Experimental values of plasma electrical conductivity are in reasonable agreement with theory.

The Doppler Effects of the Drifting Plasma in Semiconductors

The Doppler effects of injected carriers of semiconductor are detected in microwave fields and applied to the measurement of the drift velocity of semiconductor plasma. The beat frequency (Δf) between incident and Doppler shifted microwave signals is theoretically shown to be given by Δf=(2vd/cp)f0, where vd and cp are the drift velocity of injected carrier and the phase velocity of electromagnetic wave of frequency f0 in a wave guide, respectively. This relation is verified experimentally by the observation of the Doppler signals in 35 G.c/s as well as by the measurement of the drift time between two tapered wave guides of 10 G.c/s. The drift velocity of the injected carriers can be measured over a wide range of electric field strength. In lower electric field strengths the drift velocity is equal to the ambipolar drift velocity, but in high electric fields it deviates from the ambipolar velocity and finally saturates to a constant value.

Stark Effect and Hyperfine Structure of Hydrogen Fluoride

The nuclear hyperfine structure constants and the electric dipole moment of hydrogen fluoride, ${\mathrm{H}}^{1}$${\mathrm{F}}^{19}$, in the ground-vibration and first excited rotation state have been measured in a molecular beam electric resonance experiment. The hfs constants are: ${c}_{\mathrm{F}}=307.6\ifmmode\pm\else\textpm\fi{}1.5$ kc/sec, ${c}_{p}=\ensuremath{-}70.6\ifmmode\pm\else\textpm\fi{}1.3$ kc/sec, $\frac{2}{5}\frac{{g}_{p}{g}_{\mathrm{F}}{{\ensuremath{\mu}}_{\mathrm{nm}}}^{2}}{h〈{r}^{3}〉}=57.6\ifmmode\pm\else\textpm\fi{}0.44$ kc/sec. The apparatus was calibrated by observing Stark transitions in the ground-vibration and first excited rotation state of carbonyl sulfide, ${\mathrm{O}}^{16}$${\mathrm{C}}^{12}$${\mathrm{S}}^{32}$, which gave $\frac{{\ensuremath{\mu}}_{\mathrm{HF}}}{{\ensuremath{\mu}}_{\mathrm{OCS}}}=2.554\ifmmode\pm\else\textpm\fi{}0.0037$, or ${\ensuremath{\mu}}_{\mathrm{HF}}=1.8195\ifmmode\pm\else\textpm\fi{}0.0026$ D, by using ${\ensuremath{\mu}}_{\mathrm{OCS}}=0.7124\ifmmode\pm\else\textpm\fi{}0.0002$ D. An absolute measurement of the OCS electric dipole moment gave ${\ensuremath{\mu}}_{\mathrm{OCS}}=0.7120\ifmmode\pm\else\textpm\fi{}0.003$ D. A digitally computed solution of the Stark effect with magnetic hyperfine structure was necessary to interpret the data. The theory and experiment are in good agreement over the range of electric-field strengths used in the experiment. The hfs constants are in excellent agreement with the averaged absolute values of these constants as measured in a molecular beam magnetic resonance experiment. The agreement has significance because of discrepancies between the results from the two resonance methods, for some other molecules, in previous experiments.

On adsorption at the oil/water interface and the calculation of electrical potentials in the aqueous surface phase. II. The effects of ionic size

An equation is derived similar to the Gouy equation for a flat diffuse double layer but which takes into acount the finite sizes of the adsorbed and counter ions. The corresponding equation giving the variation of potential with the distance from the plane of charge is derived for systems where the potential exceeds ca . 50 mV. A relation between specific surface charge and surface pressure (equation of state) is deduced on this basis for completely ionized adsorbed films. These equations are tested for films of sodium alkyl sulphates and dodecyltrimethylammonium bromide adsorbed at the petroleum-ether/water interface, allowance being made for the presence of counter-ions above the plane of the film ions. The modified equations predict the electrical potentials in the region of the interface much more completely than the simple Gouy equation. An estimate of the number of counter ions present in the region above the head groups is given and the possible effects of their presence there on surface viscosity and electrophoretic phenomena briefly considered. Other possible corrections to simple diffuse double-layer theory are discussed; it is concluded (in agreement with other recent authors) that electrical polarization and dielectric saturation effects tend to cancel out over the experimental range of electric field strengths. Fluctuation phenomena (‘self atmosphere * effects) may become important at high values of kx and in this region may cancel out the ionic size effect, so that the potential-distance relation derived from the standard Gouy-Chapman treatment should be obeyed in the outer regions of the diffuse double layer. Deviations occur from the modified Gouy equation for the shorter chain surface active agents in absence of any added electrolyte. The causes suggested are: (1) the inadequacy of the simple geometrical model used for determining the film ion size correction; (2) the inapplicability of the expression used to calculate bulk phase activity coefficients for detergents at high concentrations.