Polyculture of scallopChlamys farreri and kelpLaminaria japonica in Sungo Bay

Several polyculture models of scallopChlamys farreri and kelpLaminaria japonica currently employed in Sungo Bay and other parts of northern China are described in this paper. Economic benefits of different polyculture models are analysed based on the growth rate, culture density and market price. In addition, site selection, critical environmental conditions and polyculture problems are discussed in detail. This project was funded by the International Development and Research Centre (IDRC), Canada, and the National Committee of Science and Technology of China.     

A variational inequality approach to free surface seepage in an inhomogeneous dam

The current work uses Baiocchi's transformation to obtain heuristically a formulation of the inhomogeneous dam problem. When finite element methods are applied the finite dimensional problem is a variational inequality which may be solved to obtain approximate solutions. The main advantage of the method is that it uses a fixed mesh. The finite dimensional problem is solved by means of succesive overrelaxation with projection. Although the standard convergence theory¹ for this method does not apply in this case, because the stiffness matrix is not symmetric, satisfactory and rapid convergence was obtained in all of our examples. Numerical results are given for some examples.     

Structure-composition relations and Raman spectroscopy of high-pressure sodium silicates

?-Na₂Si₂O₅, ζ-Na₂Si₂O₅, Na₂Si[Si₂O₇], and Na₆Si₃[Si₉O₂₇] have been synthesized using an MA6/8 superpress. Densification in high-pressure sodium silicates is effected largely by changes in packing. In the relaxed (1 bar) structures, cation polyhedra and thermal/displacement parameters are similar to those of low-pressure silicates, but the extra-framework cation positions are oversized. The two mixed ^[4]Si and ^[6]Si framework silicates of known structure (Na₂Si[Si₂O₇] and Na₆Si₃[Si₉O₂₇]) belong to the limited homologous series Na_2mSi_m[Si_n–mO_2n+m], with m<n. The structure-composition relationships of wadeite-type, A₂Ge₄O₉-type, and Na₆Si₃[Si₉O₂₇] silicates and germanates depend on T-O distance and size of the large extra-framework cation. Characteristic features of the SiO₄ tetrahedral units are present in micro-Raman spectra of mixed ^[4]Si and ^[6]Si framework silicates, but bands uniquely attributable to SiO₆ octahedra are weak or obscured. However, ^[6]Si has a profound indirect influence on the Raman spectra, resulting in intense and complex low-frequency bands, assigned to symmetric bending modes with coupled displacements at both bridging oxygens and nonbridging oxygens bonded to ^[6]Si, and a shift to higher frequency and reduction in intensity of the high-frequency bands assigned to symmetric ^[4]Si-O_nbr stretching vibrations. Raman spectroscopy does not appear to be a useful structural probe for small amounts of ^[6]Si in silicate glasses and melts.     

Contaminants in sediments: Using robust regression for grain-size normalization

Sediment contaminant concentrations usually show an inverse correlation with grain size. This can cause difficulties in distinguishing real differences in contamination from artifacts caused by variations in sediment texture. To overcome this, regression analysis is frequently used to remove the dependency of concentrations on grain size. However, least squares regression lines can be affected markedly by the presence of a small number of unusual samples in the dataset. These outliers may represent samples which are more severely contaminated or which were derived from areas with different underlying geology. They can be removed semi-manually, but robust regression methods such as least absolute values provide a convenient and objective alternative. The methods are illustrated using an example dataset of metal contaminants in sediments from the Humber Estuary, United Kingdom. Least squares regression on the complete dataset yields a rather poor grain size normalization for several elements. By contrast, least absolute values regression produces results very similar to those obtained by least squares regression after careful manual removal of outliers, but it avoids the need for subjective judgments of which data points to omit from the analysis. The intercepts of several of the fitted regression lines were non-zero, indicating that regression-based normalization is preferable to methods based on ratios.     

‘We promise you a warm welcome’: tourism to Malta since the 1960s

Tourism is an important element in the Malta economy. This paper traces its development since the 1960s with discussion focussing on the nature of the tourism product, marketing initiatives, arrivals patterns and changes in the accommodation sector. Problems such as an over-dependence on British visitors, the inadequacies of the infrastructure and the limited impact of planning are highlighted. Recent efforts to improve the quality of Maltese tourism are reviewed.     

High resolution provenancing of long travelled dust deposited on the Southern Alps, New Zealand

On 7 February 2000 an atypical orange discolouration of snowfields in the central Southern Alps, New Zealand occurred following the passage of a cold front. Analysis of snow samples identified fine orangey-brown dust mixed with much coarser grey dust. Air parcel forward trajectories from dust sources in southern and central Australia, where dust storms were reported on 4 February 2000, were computed to identify the deposits source. Geochemical analyses of the dust deposit using 26 trace elements, unaffected by regional air pollution and gravitational sorting, indicate that 20% of the dust was sourced from western New South Wales, with 45% from the eastern Eyre Peninsula of South Australia and the remaining 35% was local New Zealand dust. This provenancing approach provides a spatial resolution of long travelled dust sourcing not previously achieved.