Detailed information is given on an experiment which was carried out to investigate the spin-dependent attenuation of electron beams transmitted through a vapour of chiral molecules. The experiment is considered to be the first verification of electron dichroism. A transmission asymmetry for longitudinally polarized electron beams of opposite helicity was observed for , a camphor-like molecule containing an ytterbium atom, and also recently for bromocamphor. Asymmetries of about , which is clearly above the detection limit, were measured for both targets at electron energies between 0.5 and 10 eV. No asymmetry was found when enantiomeric camphor vapour was used as the target, thus contradicting a result which has been previously published by another group. The asymmetry measurements are compared with electron transmission spectra, which show that the energies where resonant temporary-ion formation takes place and those of the extrema of the asymmetry agree to a great extent.

A fractional step method is developed for solving the time dependent two‐dimensional Euler equations with full non‐linear free‐surface boundary conditions. The geometry of the free surface is described by a height function, and its evolution is tracked by integrating in time the kinematic boundary conditions based on the free‐surface volume flux. The fluid domain is discretised by adapting a time‐varying curvilinear grid to all boundaries, including the free surface. Mass and momentum equations are discretised by a conservative finite volume formulation, taking into account the time dependency of the grid. A fractional step type method is developed for integrating the fluid motion in time. The method is applied to a non‐linear standing wave in a square container, testing for compliance with mass and energy conservation and comparing computed wave period with other results. Non‐linear travelling waves are simulated in channels with either constant depth or varying depth and non‐linear wave processes involving both triad interactions and quartet interactions are studied. Results are compared with both experimental data and theoretical results and excellent agreement is found. Interaction of waves and currents is studied. The blocking of waves in an opposing current is simulated and found to show good agreement with theoretical results. The method is intended to be a first step towards a full description of wave dynamics interacting with structures and currents. © 1998 John Wiley & Sons, Ltd.

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The mechanism of SO2 absorption in seawater is treated. Emphasis is on applications of scrubbing of marine engine exhaust gas containing SO2. The formulated model is used to predict the influence of various parameters on SO2 absorption efficiency, e.g., seawater temperature, partial pressure of SO2, seawater salinity, and seawater alkalinity. It is found that the absorption capacity of standard seawater is approximately twice that of brackish water with close to zero salinity. The absorption capacity decreases with both decreasing salinity and alkalinity. Different scenarios in which the required water supply rate for a given SO2 cleaning efficiency is calculated. It is found that a 66% cleaning efficiency, corresponding to meeting the limits of SO x emission control areas (SECA) when operating on a fuel containing 4.5% w/w sulfur, requires a minimun water supply rate of 40–63 kg/(kW h) depending on the seawater composition in terms of salinity and alkalinity. Such data are essential in judging the operating cost of seawater scrubbing compared to alternative methods.

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