Pressure and volume changes in magmatic systems due to the vertical displacement of compressible materials

The problem of a pressure or volume increase due to the vertical redistribution of two substances with differing compressibilities is considered and compared with a previous treatment. Modified expressions for the pressure and volume changes are obtained using the general equation of state with constant compressibility. The effects of gas and melt compressibilities, and also of the solubility of gas in floating bubbles, on pressure and volume changes in magmatic systems are discussed. Very different conclusions from those in the previous treatment are found.     

REVIEWS

Book reviewed in this article:
Geographic Systems: Developments and Applications, Edited by Les Worrall, New York: Belhaven Press, 1990.
The Urge to Clear the 'Bush': A Study of Native Forest Clearance on Farms in the Catlins District of New Zealand 1861–1990 By G.A. Wilson
Southeast Asia. A Region in Transition By Johnathan Rigg.
Greater Cook Strait -Form and Flow By T.F. W. Harris
Neotectonics and Resources By J. Cosgrove & M. Jones
New Zealand and International Migration: A Digest and Bibliography Number 2 Edited by Andrew D. Trlin and Paul Spoonley, Palmerston North: Department of Sociology, Massey University
Mining, Indigenous Peoples and Development in Australasia By J. Connell and R. Howitt, Sydney University Press, Sydney, NSW, 1991.
Pacific Asia By David Drakakis-Smith.
Plains of Promise, Rivers of Destiny, Water Management and The Development of Queensland 1824–1990 By J.M. Powell, Boolanong, Bowen Hills, Queensland
Dictionary of Environmental Science By G. Jones, A. Robertson, J. Forbes and G. Hollier.
Land Use Change in Modern Japan (Nihon No Kindaika To Tochi Riyo Henka) By Yukio Himiyama
Inventing Places: Studies in Cultural Geography By Kay Anderson and Fay Gale     

Nutrient conditions in the Euboikos Gulf (west Aegean)

The Euboikos Gulf is a restricted embayment on the eastern coast of Greece, having a significant, unusual tidal phenomenon, and receiving some industrial and domestic wates. The South Euboikos Gulf has only slightly greater concentrations of nutrients than background, while the North Euboikos Gulf tends to accumulate nutrients, in particular nitrate and silicate. Also a comparison is made with the nutrient concentrations in polluted coastal gulfs of the Aegean. The different nutrient levels are due to the different sources of nutrients, as well as the morphology of each area and the circulation of the waters.     

Delay coordinates: a sensitive indicator of nonlinear dynamics in single charged particle motion in magnetic reversals

The delay coordinate technique is examined as an indicator of the regime of particle dynamics for the system of single charged particle motion in magnetic reversals. Examples of numerically integrated trajectories in both static (zero electric field) and time dependent (corresponding nonzero induction electric field) simple models for magnetic reversals are considered. In the static case, the dynamics can in principle be directly classified by constructing Poincaré surfaces of section; here we demonstrate that whilst the Poincaré surface contains the relevant information to classify the dynamics, the corresponding delay coordinate plot can provide a far more sensitive indication of the onset of nonregular behaviour. In the case of nonperiodic time dependence considered here Poincaré plots cannot in general be constructed directly. Nevertheless, delay coordinate plots can still reveal details of the phase space portrait of the system, and here are shown to indicate whether segments of stochastic motion exist in a given trajectory. It is anticipated that the delay coordinate plot technique as realized here will be a valuable tool in characterizing the behaviour in large numbers of trajectories that are evolved in time-dependent systems, thereby giving us insight into the evolution of the distribution function as a whole, either in prescribed fields or in self-consistent numerical simulations.     

DDT,PCB and benzo(a)pyrene levels in white croaker (Genyonemus lineatus) from southern California

In 1978 the California Department of Fish and Game carried out a major, independent sportfishing survey in southern California. The results of that survey indicated that approximately one million angler-trip hours per year were spent fishing and that one in three fish caught was a white croaker (Genyonemus lineatus). There was no attempt by the Department of Fish and Game to determine the disposition of caught fish. We conducted a subsequent survey in 1980 which included 12 popular sportfishing sites in the Los Angeles area. Our results also indicated that one in three fish caught was a white croaker. In addition our survey showed that 82% of the sportfishermen ate the white croaker they caught and the median consumption was 14.8 g day^?1 person^?1. White croaker were then sampled by hook-and-line from 11 of the 12 survey sites plus two control sites and analysed for PCB, DDT and BaP. Median PCB levels ranged from 0.014 to 0.41 mg wet kg^?1; median DDT from 0.059 to 7.5 mg wet kg^?1 and BaP was below detectable limits of 1 ng for all sites.