(Pro)Motion Pictures: Len Lye in the Thirties

This article examines Len Lye’s film-making in the 1930s within a broader visual arts context, seeking to clarify the nature and extent of his involvement in British documentary film culture at this time. In particular, it demonstrates how Lye's method of fusing 'live action', found footage, and animation techniques created the possibility of a radical documentary practice that could reconcile promotional advertising and commercial art with avant-garde abstraction and kinaesthetic experimentation. In particular, the article focusses on Lye's N. or N.W. (1937, 35mm, b&w, 10 mns), arguing that his work from this period should be regarded as central - and not marginal - to any serious reassessment of Britain's “Documentary Movement” of the inter-war era, and its relations to any history of the cinema and visual culture.

A comparison of monkey and human motion processing mechanisms

Single-cell recording studies have provided vision scientists with a detailed understanding of motion processing at the neuronal level in non-human primates. However, despite the development of brain imaging techniques, it is not known to what extent the response characteristics of motion-sensitive neurons in monkey brain mirror those of human motion sensitive neurons. Using a motion adaptation paradigm, the direction aftereffect, we recently provided evidence of a strong resemblance in the response functions of motion-sensitive neurons in monkey and human to moving dot patterns differing in dot density. Here we describe a series of experiments in which measurements of the direction aftereffect are used to infer the response characteristics of human motion-sensitive neurons when viewing transparent motion and moving patterns that differ in their signal-to-noise ratio (motion coherence). In the case of transparent motion stimuli, our data suggest suppressed activity of motion-sensitive neurons similar to that reported for macaque monkey. In the case of motion coherence, our results are indicative of a linear relationship between signal intensity (coherence) and neural activity; a pattern of activity which also bears a striking similarity to macaque neural activity. These findings strongly suggest that monkey and human motionsensitive neurons exhibit similar response and inhibitory characteristics.

Data-driven optimal filtering for phase and frequency of noisy oscillations: Application to vortex flow metering

A method for measuring the phase of oscillations from noisy time series is proposed. To obtain the phase, the signal is filtered in such a way that the filter output has minimal relative variation in the amplitude over all filters with complex-valued impulse response. The argument of the filter output yields the phase. Implementation of the algorithm and interpretation of the result are discussed. We argue that the phase obtained by the proposed method has a low susceptibility to measurement noise and a low rate of artificial phase slips. The method is applied for the detection and classification of mode locking in vortex flow meters. A measure for the strength of mode locking is proposed.

Detection of improper installation from the sensor signal of vortex flowmeters

Effects of inappropriate installation can bias the measurements of flowmeters. For vortex flowmeters, a method is proposed to detect inappropriate installation of the flowmeter from the oscillatory signal of the vortex sensor. The method is based on assuming the process of vortex generation to be a generic, noisy, nonlinear oscillation, describable by a noisy Stuart-Landau equation, with a corresponding sensor signal that also contains higher harmonic excitations. By making use of the scaling properties of the Navier-Stokes Equation, the method was designed to be robust with respect to uncertainties in the fluid properties. The diagnostic functionality is demonstrated on measurement data. In the experiments, installation effects that lead to more than 0.5% error in the output of the flowmeter could clearly be detected. (C) 2003 Elsevier Ltd. All rights reserved.

Nonlinear theory of solitary waves associated with longitudinal particle motion in lattices - Application to longitudinal grain oscillations in a dust crystal

The nonlinear aspects of longitudinal motion of interacting point masses in a lattice are revisited, with emphasis on the paradigm of charged dust grains in a dusty plasma (DP) crystal. Different types of localized excitations, predicted by nonlinear wave theories, are reviewed and conditions for their occurrence (and characteristics) in DP crystals are discussed. Making use of a general formulation, allowing for an arbitrary (e.g. the Debye electrostatic or else) analytic potential form phi(r) and arbitrarily long site-to-site range of interactions, it is shown that dust-crystals support nonlinear kink-shaped localized excitations propagating at velocities above the characteristic DP lattice sound speed v(0). Both compressive and rarefactive kink-type excitations are predicted, depending on the physical parameter values, which represent pulse- (shock-)like coherent structures for the dust grain relative displacement. Furthermore, the existence of breather-type localized oscillations, envelope-modulated wavepackets and shocks is established. The relation to previous results on atomic chains as well as to experimental results on strongly-coupled dust layers in gas discharge plasmas is discussed.

Vortex shedding and drag in dilute Bose-Einstein condensates

Above a critical velocity, the dominant mechanism of energy transfer between a moving object and a dilute Bose-Einstein condensate is vortex formation. In this paper, we discuss the critical velocity for vortex formation and the link between vortex shedding and drag in both homogeneous and inhomogeneous condensates. We find that at supersonic velocities sound radiation also contributes significantly to the drag force.

Dissipation and vortex creation in Bose-Einstein condensed gases

We solve the Gross-Pitaevskii equation to study energy transfer from an oscillating