Intermittent electric fields

Intermittent electric fields have been suggested in the past as a way to reduce the average molecular orientation during an experiment, with... 

Some researchers [121, 126, 139] have demonstrated that intermittent application of AC or DC electric fields across MF or UF membranes during filtration can often promote displacement of polarization- or adherent fouling layers, with significant improvements in sustained permeation flux. The electrode is installed on either side of the membrane with the cathode on the permeate side and the anode on the feed side. Usually, the membrane support is made of stainless steel or the membrane itself is made of conductive materials to form the cathode. Titanium coated with a thin layer of a noble metal such as platinum could be one of the best anode materials [140], The electromagnetic field reduces fouling and biofilm development. 

Microtox is used in the field to screen water samples rapidly, even in areas where intermittent electricity supplies may preclude the use of more conventional techniques. The use of Microtox is one of screening to monitor signs of toxicity [35]. Chemical analysis would need to be undertaken if long-term use of a water source were required. Alternative bioassay (fathead minnows, trout, Daphnia magna, etc.), arc unsuitable for field use and requires 48 — 72 h to produce results. 

There is an indirect way to detect intermittent local collective motions. In the case of depolarized Raman scattering, the depolarization ratio is sensitive to low-frequency fluctuations in water. Depolarization is the scattering of the polarization of the electric field of light in a direction perpendicular to the original direction of polarization. Each fluctuating state has a distinct depolarization ratio. The intermittent character of the dynamics is known to appear as a so-called 1,/ frequency (f) dependence in a power spectrum. The power spectmm is obtained by Fourier transforming a time correlation function. 

The electron diffusion coefficient D E) from the electric field in the single-walled zigzag CNT with adsorbed hydrogen atoms has a pronounced nonlinear character (Fig. 1.5). Increase of the field leads to an increase in first rate, and then to his descending to a stationary value. This phenomenon is observed for all systems with intermittent and limited electron dispersion law [17]. Electron diffusion coefficient can be considered constant in the order field amplitudes E 5x10 V/m. The maximum value of the diffusion coefficient for semiconductor CNTs observed at field strengths of the order ofE- 4.8x10 V/m. 

Holes (in electrical conductivity). The absence of an electron from a compound or crystal structure leaves a hole. Holes move through the crystal or compound under the action of an electric field, in the opposite direction to that taken by electrons. They thus behave much like electrons, but carrying positive charge. Holey Boy. A type of perforated floor in intermittent downdraught kilns firing salt-glazed pipes. 

In order for ER fluids to be used in various devices, it is necessary that (i) the induced shear stress be large (stress properties) (ii) the current density be small (current properties) (iii) when an electric field is continuously or intermittently applied the induced shear stress or current density does not change as a fimction of time (electrical permanence) (iv) viscosity without electric field application be small (flow properties) and (v) the stability of the suspended particles be high (suspension stability) [72]. 

One of the first techniques that has been suggested in an attempt to improve the separation of larger (K>50 kbp) DNA fragments relied on intermittent electric fields35,47-49 where the field E is on for pulses of duration separated by zero-field pulses of duration The large... 

Fig.11 Result of a computer simulation of the BRM The electrophoretic velocity is plotted as a function of the molecular size N (in segments) for a scaled electric field of 0=1.0. The dashed line is for a continuous field and has a minimum at AT l4. The solid curve is for intermittent fields with qj =(1/8) opp=200Xbi, and has a minimum for N 20.

At higher temperatures the clusters become smaller and more ramified. The percolating cluster can be destroyed temporarily by thermal motion. Indeed, at ksT = 0.65 we observe intermittent behaviour (see fig. 4). Fig. 5 shows the conductivity as a function of the electric field at the latter temperature. The measured points are fitted with... 

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