Aims and implementation in British urban and regional planning

Failure to fully understand or recognise crucial but culturally-determined British dimensions has led to confusion and error even among the British geographers in understanding and contributing to, urban and regional planning. This point assumes more rather than less significance in the context of a discussion between British and Soviet geographers. This paper therefore examines in part one, three fundamental features of the British system of urban and regional planning and then proceeds in part two to focus on the aims and their implementation. It concludes with a reference to the nature of the relationship between planning and geography.     

A two-dimensional photochemical model of the stratosphere with Rayleigh scattering

Computations of concentrations of minor stratospheric gases using a two-dimensional model of the stratosphere are reported. The model includes Rayleigh scattering. This results in an increase in the photodissociation rate computation time by a factor of 1.5. The effect of ground albedo is assessed by comparing our results with a calculation of photolysis rates for a constant albedo with latitude. Comparison of results with a reference model including only molecular absorption are also made. The largest differences (50%) occur in NO and OH. An approximate expression for including the effects of Rayleigh scattering and surface reflectance in multi-dimensional models is suggested.     

Strontium isotopic geochemistry of intrusive rocks,Puerto Rico,Greater Antilles

The strontium isotopic geochemistry is given for three Puerto Rican intrusive rocks: the granodioritic Morovis and San Lorenzo plutons and the Rio Blanco stock of quartz dioritic composition. The average calculated initial⁸⁷Sr/⁸⁶Sr ratios are 0.70370, 0.70355 and 0.70408, respectively. In addition, the San Lorenzo data establish a whole-rock isochron of71 ± 2m.y., which agrees with the previously reported K-Ar age of 73 m.y. Similarity of most of the intrusive rocks in the Greater Antilles with respect to their strontium isotopic geochemistry regardless of their major element composition indicates that intrusive magmas with a wide range of composition can be derived from a single source material. The most likely source material, in view of the available isotopic data, is the mantle wedge overlying the subduction zone.     

Tests for size and shape dependency in deep-sea mixing

Bioturbation is generally not a strongly size-dependent or shape-dependent process in deep-sea sediments. Different sizes of ash (11–250 μm) deposited during a single eruption are usually mixed about equally, although in a few cores we found minor tendencies toward greater mixing of finer ash. Platey volcanic ash and spherical microtektites initially deposited within a few centimeters of each other in the sediment column are mixed with roughly comparable intensity. Radiocarbon dating of three sizes of CaCO₃ near the top of one box core produced ages within the analytical error; this also suggests no size dependency in the mixing process. Another core showed age differences opposite in sense to those that would be predicted if the finer fractions were more intensely mixed than the coarser fractions.The sizes examined (11–250 μm) encompass most of the sedimentary components used in paleoclimatic analyses of deep-sea cores. From these findings, we infer that significant artificial lead/lag offsets in paleoclimatic signals will not be created by size-selective or shape-selective mixing. Mixing models calibrated on one sediment size fraction should be generally applicable to other sizes and kinds of material.     

Stable isotope studies of fluid inclusions in speleothems and their paleoclimatic significance

Fluid inclusions found trapped in speleothems (cave deposited travertine) are interpreted as samples of seepage water from which enclosing calcium carbonate was deposited. The inclusions are assumed to have preserved their D/H ratios since the time of deposition. Initial ¹⁸O/¹⁶O ratios can be inferred from δD because rain- and snow-derived seepage waters fall on the meteoric water line (δD = 8δ¹⁸O + 10). Estimates of temperature of deposition of the carbonate can be calculated from inclusion D/H ratios and δ¹⁸O of enclosing calcite in Pleistocene speleothems. For most speleothems investigated (0–200,000 yr old) δ¹⁸O of calcite appears to have decreased with increasing temperature of deposition indicating that the dominant cause of climate-dependent change in δ¹⁸O of calcite was the change in K_cw, the isotope fractionation equilibrium constant, with temperature; δ¹⁸O of meteoric precipitation generally increased with increasing temperature, but not sufficiently to compensate for the decrease in K_cw.     

A numerical study of the topographic effect on electromagnetic fields in a three-dimensional conductivity model

Summary The topographic effect on electromagnetic fields in a three-dimensional conductivity model is investigated using a finite-difference numerical method. The model is that of a conducting block buried in the host Earth beneath a conducting hill. The altitude effect as well as the effect of conductivity of the hill has been studied by comparing the results for the field components at the surface of the hill with those at the surface of a flat half-space. The results indicate that both altitude and the hill conductivity influence the behaviour of the electromagnetic fields. For certain traverses beyond the edge of the block, it is seen that the variations in some field components are mainly due to the topographic effect and that the contribution from the block itself is negligible.