Transient Interference Research Articles

Infrared recording of transient and permanent interference gratings with commercial plastics

Two commercial plastics have been used to record infrared interference patterns when a CO(2) laser is used as a light source. Recording of transient and permanent interference gratings with different spatial frequencies was carried out. The diffraction efficiency for red light as a function of time for different exposure times is shown; maximum diffraction efficiencies attained were of the order of 30%. The possibility of using one of these plastics as an optical switch is shown.

Theory of induced spatial incoherence

This paper describes theoretical and experimental investigations of induced spatial incoherence (ISI), a technique for achieving the smooth and controllable target beam profiles required for direct-drive laser fusion. In conventional ISI, a broadband laser beam (coherence time tc=1/Δν≪tpulse) is sliced into an array of mutually incoherent beamlets by echelon structures that impose successive time delay increments Δt>tc. A focusing lens then overlaps those beamlets onto the target, which is usually located at the far field. Here, we evaluate the ideal target beam profiles for practical ISI focusing configurations, and examine the perturbing effects of transient interference, laser aberration, and plasma filamentation. Analytic and numerical calculations show that nonuniformities due to interference among the beamlets are smoothed by both thermal diffusion and temporal averaging. Under laser-plasma conditions of interest to inertial confinement fusion (ICF), average ablation pressure nonuniformities ∼1% should be readily attainable. We also investigate a partial ISI scheme, which allows widely spaced beamlets to remain mutually coherent; the resulting high spatial frequency interference structure can be effectively smoothed by thermal diffusion alone. A perturbation analysis shows that the average target profile 〈I(x)〉 remains relatively insensitive to laser beam aberration when the scale length of that aberration is larger than the initial beamlet width. This aberration will tend to broaden and smooth 〈I(x)〉, rather than introduce any small-scale structure. The broadening is largely controllable because it depends only upon spatial averages of the aberrated quantities over the entire laser aperture; the uncontrollable perturbations can be reduced to ∼1% in practical cases. Filamentation in the underdense plasma has been studied numerically using a 2D propagation/hydro code selfoct, which includes both ponderomotive and thermal effects. For 0.25-μm light, this code predicts that ISI should suppress filamentation in plasmas of interest to ICF. We review recent planar target experiments carried out at the Naval Research Laboratory using 1.054- and 0.527-μm light, which show that the combination of ISI and shorter wavelength substantially reduces all evidence of plasma instabilities. Finally, we review a promising alternative technique for achieving ISI in KrF lasers without using echelons.

The Action of Divalent Zinc, Cadmium, Mercury, Copper and Lead on the Trans-Root Potential and H+, Efflux of Excised Roots

Kennedy, C. D. and Gonsalves, F. A. N. 1987. The action of divalent zinc, cadmium, mercury, copper and lead on the trans-root potential and H+ efflux of excised roots.—J. exp. Bot. 38: 800–817. The action of Zn2+, Cd2+, Hg2+, Cu2+ and Pb2+ ions on the trans-root potential and H+ efflux of young excised maize roots has been studied. Micro-electrode implantations into root epidermal cells confirmed the root outer membranes as the major contributor in the trans-root potential changes. The effects of these ions on H+ efflux were studied over a period of time in a continuous flow cell apparatus, adequate controls allowing for transient interference due to divalent cations at the pH probe. The addition of Zn2+, 5 to 100 μmol dm−3, to the solution bathing the roots reduces H+ efflux and depolarizes the trans-root potential. However, in the presence of Mg2+, 0·1 or 1·0 mmol dm−3, not only is this depolarization inhibited, but hyperpolarization is observed instead. Cd2+ affects trans-root potential and H+ efflux at a much slower rate than Zn2+, suggesting a lower membrane permeability. Without Mg2+, Cd2+ hyperpolarizes the trans-root potential, but this is better sustained in its presence. Hyperpolarization did not occur with Hg2+, Cu2+ or Pb2+ whether or not Mg2+ was present Hg2+ and to a lesser extent Cu2+ are potent depolarizers of the trans-root potential and strongly inhibit H+ efflux. The maximum rates of depolarization observed in the absence of Mg2+ increase in the order Cd ≈ PCMBS ≪.lt; Zn ≈ Cu < Hg. This is similar to the relative maximum rates of H+ inhibition, Pb ≈ Cd ≪.lt; Zn < Cu < Hg, suggesting considerable differences in mode of action and/or membrane permeability. The lower membrane permeability of the sulphydryl reagent PCMBS apparently prevents ready access to the site(s) of action available to Hg2+. The reductions in trans-root potential and H+ gradients induced by this range of cations would be detrimental to the acquisition of nutrients using these gradients as an energy source. In contrast, Zn2+, , in the presence of adequate Mg2+, could be beneficial to nutrient uptake by maintaining a higher membrane potential than would occur in its absence. Possible modes of action for the observed effects are discussed.

Transient interference gratings and holograms in dyed plastic

Transient diffraction gratings were holographically made in dyed plastic by absorbing laser light. Mean energy values of 40 mJ/cm2 absorbed in a 3-mm thick layer were needed to make gratings that lasted about 10 s. The writing beams and a reading one of different wavelength were simultaneously made to fall on the plastic: the reading beam was diffracted by the grating, which produced transient diffracted beams of sufficient intensity to be seen by the naked eye or to be stored permanently by conventional photographic methods. Curves showing diffraction efficiency versus exposure with grating frequency as a parameter are presented. Applications to real-time single and double exposure holography are also discussed.

Electromagnetic Compatibility of Marine Computer System

Germanischer Lloyd, one of nine internationally recognized Ship Classification Societies, is at present participating in a project aimed at the “Development of a New Technique for Ship Operation”. The objective of the project is to raise the technological level of the ship as a transportation system, with the aid of todays’ scientific and technological potential. This means that the construction of seagoing ships of all kinds is intended to result in more economical ships by using-a high degree of automation-a high standard of safety-a high degree of reliability-optimum utilization of primary energy for propulsion and operation systems.Ships must be absolutely self-contained and self-supporting during voyages. The space available on board is limited and frequently the installation of different systems has to be confined to special areas of the ship. This necessarily results in mixed installations and unpredictable ambient conditions.One of the problems implied is electromagnetic compatibility. With the assistance by the Federal Minister of Research and Technology, the Electrotechnical Division of Germanischer Lloyd has undertaken studies in this field which were aimed at:1.Determination of the interference levels aboard ships2.Determination of the required susceptibility of instruments on board3.Specification of methods and instruments for EMC measurements4.Regulations for the installation of instruments and systemsThe present paper deals with the first three items and is based on comprehensive measurements carried out aboard a 4th generation container ship with a deadweight of approx. 50.000 tdw. The results obtained were compared to corresponding measurements obtained from a passenger vessel of 34.000 tdw and a chemical products carrier of 27.000 tdw. The results presented relate mainly to stationary, but also to transient interference levels in the ship's mains and essentially to control and signal lines of automation systems.

Geological Evaluation of Fractured Reservoirs: ABSTRACT

Effective evaluation of fractured reservoirs involves both qualitative and quantitative data of various levels of complexity. This paper attempts to describe those geological and petrophysical data necessary in making an early evaluation of a fractured reservoir, during either exploration or early development phases. As such, prediction rather than detection will be emphasized. Early in the evaluation of a fractured reservoir the majority of predictions are based on direct observations of a combination of geological and rock data. Those observations are generally made by geologists and/or petrophysicists, and are used to determine: (1) fracture origin and distribution, (2) the reservoir characteristics of the fracture system, (3) the interaction of the fracture and matrix porosity systems, and (4) the type of fractured reservoir, based on the contribution of the fracture system to overall reservoir quality. Each of these determinations is discussed, including the general types of geological interpretations End_Page 1681------------------------------ and rock property analysis required. Subsequent to those early determinations and predictions by geologists, larger scale, more quantitative data detecting the effect of reservoir fractures are made by the reservoir engineers. Techniques such as pressure transient analyses and interference testing allow the extrapolation of small scale geological and petrophysical data to larger scale reservoir flow predictions using large mathematical reservoir flow models. End_of_Article - Last_Page 1682------------

Transient Interference Phenomena in Collinear Fast-Ion-Beam Laser Spectroscopy

By introducing a Doppler switching technique in collinear fast-ion---beam laser spectroscopy, transient interference phenomena were observed. The shape of the experimental spectra can be related to the Fourier analysis of the evolution in time of the laser frequency, as probed by the ions.

Interference with ingestional aversion learning produced by preexposure to the unconditioned stimulus: Associative and nonassociative aspects

Preconditioning exposure to a lithium chloride unconditioned stimulus (US) interferes with the subsequent conditioning of a taste aversion. Multiple US preexposures produce a long-lasting or durable interference with aversion learning, whereas a single US exposure produces a transient interference effect. The present experiments demonstrate that the durable US preexposure effect is substantially reduced if the method of drug treatment (infusion versus injection of the drug into the peritoneal cavity) or the spatial cues present during drug treatment (home cage versus a distinctive environment) are changed between the preexposure and taste conditioning phases of the experiment. In contrast, these manipulations do not attenuate the proximal/transient US preexposure effect. These findings indicate that different mechanisms are responsible for the two US preexposure effects. The results are consistent with previous suggestions that the durable effects of lithium preexposure are due to associative interference produced by the exteroceptive stimuli that accompany drug administrations and indicate that the proximal/transient US preexposure effect is mediated by nonassociative mechanisms.

Fourier-series techniques applied to distance protection

For distance-relay applications, the fundamental system impedance as seen from the relaying point is used as the basis for the decision to give the trip signal. This system impedance can be calculated from knowledge of the fundamental frequency components of the voltage and current waveforms, these, in turn, being determined by processing appropriate waveforms sampled at the relay point. Fourier-series analysis is one method suitable for processing the sampled waveforms and for determining their fundamental components. The analysis is designed for continuous, periodic waveforms and, in these circumstances, separates the various harmonic components of the waveform. Its behaviour under the nonperiodic conditions of fault incidence and transient interference will be demonstrated.

Nontransient learned helplessness

Dogs who receive repeated, spaced exposure to inescapable electric shock in a Pavlovian hammock fail to escape shock in a shuttle box I week later, while one session of inescapable shock produces only transient interference. Cage-raised beagles are more susceptible to interference produced by inescapable shock than are mongrels of unknown history. These results are compatible with learned helplessness and contradict the hypothesis that failure to escape shock is produced by transient stress.

Transient Interference Studies of Passively Q-Switched Ruby-Laser Emission

An experiment has been performed to examine the time variation of the position and visibility of a transient interference pattern from a single-mode, passively Q-switched ruby laser. A blue shift in the emission frequency as a function of time is observed. The power-dependent rate of frequency shift is 3.4 MHz/nsec·MW. This frequency shift is consistent with the results from previous experiments with a normally spiking ruby laser. A model is proposed which correlates the change in optical length of the ruby to changes in population inversion during emission. Predictions based on the model are in agreement with experimental results and with previous work.

Transient Interference Studies of Emission from a Pulsed Ruby Laser

A transient interference experiment has been performed using the radiation from a normally spiking, pulsed ruby-laser oscillator. In the experiment the laser output at time t is made to interfere with emission corresponding to an earlier time, t-τ, by means of an optical delay inserted into a two-pinhole Young's interferometer. A light-pipe photomultiplier oscilloscope system permits photographic recording of the interference fringes during a single spike of the laser emission, with a time resolution of less than 15 nsec. From the data obtained both the fringe visibility and the relative pattern phase of the interference pattern may be evaluated. Data are presented for both visibility and pattern phase for several delay times. The principal observation is that during a single laser spike the frequency increases with time. An analysis of the experiment and of possible causes for frequency variation of the laser with time results in the hypothesis that there is lattice strain in the ruby associated with the optical pumping to the excited state from which laser emission occurs. Linearity is assumed between strain and the number of excited ions. This permits a calculation to be made of the frequency change resulting from the strain and very reasonable agreement is obtained upon comparison with experiment. The visibility data are discussed but quantitative conclusions cannot be drawn.

A Broadband Multichannel for Improved Interference Control Transient Monitoring System

Present instrumentation for monitoring transient interference is in some respects inadequate. So are present measurement techniques. There is a need today for new instrumentation and improved techniques for measuring and recording transients. This paper describes a broadband, multichannel transient monitoring system being studied by Stoddart engineers. The system can monitor transient interference on from twelve to thirty-six different circuits simultaneously. Each circuit is monitored by an individual instrumentation channel. The design of the system is flexible enough that other channels can be added where needed. Before describing the system design philosophy, a brief review is given of the characteristics of transient waveforms. Particular emphasis is placed on transients which are normally regarded as interference. Also considered are the effects of transient interference on various types of electronic equipment. Present methods of measuring transient interference are described, and the inherent shortcomings of these techniques are pointed out. The limitations of transient monitoring devices in use today are discussed, and so is the need for new equipment and improved techniques. The discussion then leads into a detailed description of the transient monitoring system under study by Stoddart. The final design of the transient monitoring system is not yet firmly established. Nevertheless, the general design approach described in this paper offers a straightforward but practical solution to a complicated RFI problem --- that of monitoring transient interference on a large number of circuits with speed and accuracy.

Quantum Theory of Interference Effects Produced by Independent Light Beams

The conditions are examined under which interference effects should be observable in the superposition of two light beams derived from independent sources. The quantum-mechanical description of these effects differs from the classical description principally in that it is necessarily based on expectation values of the light intensity at one or more space-time points. It is shown that pure states of the radiation field which are not energy states give rise to interference effects, but in that case the two beams cannot meaningfully be described as statistically independent. For a realistic description mixed states have to be introduced, when the expectation value of the intensity gives no indication of interference effects. On the other hand, the intensity correlation at two space-time points is a periodic function of the separation of the points and indicates the presence of transient interference effects. The effects become readily observable only when the average photon occupation number of each cell of phase space is appreciably greater than 1, and this explains why laser beams were needed for the experimental observations. It is pointed out that, even in these experiments, each photon may be regarded as interfering only with itself.

Experimental Investigation of Transient Interference from Power Line Faults on Carrier Current Equipment with Reference to Relaying

Experimental Investigation of Transient Interference from Power Line Faults on Carrier Current Equipment with Reference to Relaying

A Transient Interference Dissociation with High Auricular and Ventricular Rates in a Subject already Having a Prolonged A-V Conduction Time

A Transient Interference Dissociation with High Auricular and Ventricular Rates in a Subject already Having a Prolonged A-V Conduction Time

THE INHIBITION OF GROWTH BY 1·2 : 5·6 DIBENZANTHRACENE AND OTHER AGENTS

1. Single injections of 5, 10, and 20 mg. 1·2 : 5·6 dibenzanthracene produce a prolonged inhibiting effect on the growth of young rats, and the effect produced varies as the dosage.2. Mercury in oil, bismuth salicylate in oil, and thallium acetate in single injections produce an immediate but transient interference with growth.3. Various non‐carcinogenic polycyclic hydrocarbons produce an immediate but transient interference with growth.4. Nearly half (21/48) of the animals injected with d.b.a. died within 64 days. Half the deaths (11/21) occurred between 40 and 64 days after injection.This work was made possible by a grant from the Medical Research Council for the maintenance of animals and laboratory expenses, and by a personal grant from the Cancer Control Organisation for South‐East Scotland. Thanks are also due to Dr. C. M. Scott for advice and assistance.

Transient Oscillations in Electric Wave-Filters

THE electric wave-filter has been very fully discussed with respect to its remarkable steady-state properties. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> In the present paper it is proposed to give the results of a fairly extensive t heoretical study of its behavior in the transient state. This study is of particular interest and importance in connection with the wave-filter, because, as we shall find, its remarkable selective characteristics are peculiarly properties of the steady state and become sharply defined only as the steady state is approached. To this fact, it may be remarked in passing, is to be ascribed the uniform failure of wave-filters to suppress irregular and tran sient interference, such as “static,” in anything like the degree with which they discriminate against steady-state currents outside the transmission range. This limitation is common to all types of selective networks and restricts the amount of protection it is possible to secure from transient or irregular interference. In fact the general conclusions of the present study are applicable to all types of selective circuits.