Urban development in the world dryland regions: Inventory and prospects

Interest in the social, technical and demographic problems involved in the development of the world's dryland regions has increased greatly in the recent past. This paper examines the location, size differentiation and growth of urban agglomerations with 100,000 or more inhabitants situated in the extremely arid, arid and and semi-arid regions. A total of 355 such major urban settlements are identified and their distribution and size characteristics are examined. Subsequently, the growth rates recorded by these urban areas in the period 1950–1970 are analyzed at the global, continental and national levels and according to city size. It is estimated that 26.1% of all dryland denizens reside in urban areas with populations of 100,000 or more. In conclusion, the future prospects and planning implications of such dryland urban agglomerations are discussed.     

An equation correlating the solubility of quartz in water from 25° to 900°C at pressures up to 10,000 bars

The solubility of quartz in water from 25° to 900°C at specific volume of the solvent ranging from about 1 to 10 and from 300° to 600°C at specific volume of the solvent ranging from about 10 to 100 is given by an empirically derived equation of the form: log m = A + B(log V) + C(log V)² where m is the molal silica concentration, V is the specific volume of pure water, and A = ?4.66206 + 0.0034063T + 2179.7T^?1 ? 1.1292 × 10⁶T^?2 + 1.3543 × 10⁸T^?3B = ?0.0014180T— 806.97T^?1C = 3.9465 × 10^?4T T is temperature in kelvins. The experimental data used in formulating the empirical relation ranged in pressure from 1 bar at 25°C to about 10,000 bars at 900°C, and the lowest pressure in the low-density steam region was about 30 bars. According to the above equation, the average difference in molality between 518 measured and calculated solubilities is ?0.016 m with a standard deviation of 0.089.     

Radio observations of interplanetary magnetic field structures out of the ecliptic

New observations of the out-of-the ecliptic trajectories of type III solar radio bursts have been obtained from simultaneous direction finding measurements on two independent satellite experiments, IMP-6 with spin plane in the ecliptic, and RAE-2 with spin plane normal to the ecliptic. Burst exciter trajectories were observed which originated at the active region and then crossed the ecliptic plane at about 0.8 AU. We find a considerable large scale north-south component of the interplanetary magnetic field followed by the exciters. The apparent north-south and east-west angular source sizes observed by the two spacecraft are approximately equal, and range from 25° at 600 kHz to 110° at 80 kHz.     

'Black skins–white masks': Postcolonial reflections on 'race', gender and second generation return migration to the Caribbean

This paper illustrates the opportunities afforded by the adoption of postcolonial discourse in development geography, drawing specifically on issues of transnationalism, hybridity and inbetweeness. The utility of such notions and associated approaches is illustrated by the authors' current research on the migration of young, second generation and foreign-born 'Bajan-Brits' to the small Caribbean island nation of Barbados, the homeland of their parents. Focussing on issues of 'race' and gender, the paper examines the experiences of return migration among this cohort from an interpretative perspective framed within postcolonial discourse. It argues that notwithstanding the considerable sociocultural problems of adjustment encountered, these Bajan-Brit 'returnees' may be seen as occupying positions of relative economic privilege. Theirs is a liminal space derived by virtue of having been born and/or raised in the UK and being of the black 'race'. Accordingly, they are demonstrated to be both advantaged and disadvantaged; both transnational and national; and black but, in some senses, symbolically white.     

The skylab lunar multispectral scanner data

Skylab S-192 multispectral scanner data, in 12 bands covering wavelengths from 0.41 to 2.3 μm, have been investigated to identify and classify geologic units of the lunar surface. Seventeen spectral cluster classes have been identified, seven in the highlands, seven in the maria, and three of which occur in both or in border regions. This finding may be roughly indicative of the relative heterogeneity of these regions. It implies that there is as much heterogeneity in the highlands as in the maria. This work extends the spectral and aerial coverage of similar studies of the lunar surface and provides useful data for comparison for most of the lunar near side.     

High-precision U-series measurements of more than 500,000 year old fossil corals

Robust, independent age constraints on the absolute timing of climate events based on the U-series dating of fossil coral are sparse before the last glacial cycle. Using multiple-collector inductively coupled plasma mass spectrometry with multiple-Faraday protocols, we are able to date ～ 600 ka samples with an uncertainty of better than ± 15 ka (2σ), representing a three-fold improvement in precision compared with previous techniques. Using these methods, we report U-series measurements for a suite of > 500 thousand year old (ka) corals from Henderson Island, an emergent atoll in the south-central Pacific Ocean. The fossil corals show extraordinarily little diagenetic alteration for their age and the best-preserved sample yields a U-series age of 600 ± 15 ka (2σ), which overlaps with the timing of the warm Marine Isotope Stage (MIS) 15 interglacial. The open-system model of Villemant and Feuillet [Villemant B. and Feuillet N. (2003) Dating open systems by the ²³⁸U–²³⁴U–²³⁰Th method: application to Quaternary reef terraces. Earth and Planetary Science Letters 210(1–2), 105–118.] and the linear regression (or open-system isochron) is clearly limited for such old samples. However, the open-system model developed by Thompson et al. [Thompson W.G., Spiegelman M.W., Goldstein S.L., and Speed R.C. (2003) An open-system model for U-series age determinations of fossil corals. Earth and Planetary Science Letters 210(1–2), 365–381.] appears to reliably correct for open-system effects in roughly half of the corals, giving a MIS 15 origin for these. Thus the data provide evidence that the systematic addition of ²³⁰Th and ²³⁴U through α-recoil is a dominant open-system process occurring in the Henderson Island fossil reef system. Several coral samples yield significantly older Thompson et al. open-system ages between 650 and 750 ka. The uncertainty on these ages (typically ± 30 kyrs) is too great for precise assignment but most data overlap with the MIS 17 interglacial. The reliability of these ages is currently unclear. It is shown that separate aliquots of the same coral can yield different Thompson model ages. Therefore, there appear to be additional diagenetic mechanisms that create further anomalous excursions in the U-series systematics, limiting the reliability of the Thompson et al. open-system model.     

MODALL: a practical tool for designing and optimizing capture systems

The primary goals for most ground water capture systems (i.e., pump-and-treat systems) are that (1) all contaminants within zones of interest will eventually be captured and (2) the extraction and reinjection wells are best located and operated at optimal flow rates, creating hydraulically efficient flow systems. A new tool, MODular ALLocation (MODALL), is presented to aid in the design and assessment of capture systems. MODALL uses the MODFLOW-calculated cell-by-cell flow terms to evaluate internodal flow balances to determine the percentage of flow in each cell which has either originated from a given source(s) or flows to a specified sink(s). Output from MODALL can be easily displayed in isopleths of "capture fraction" (CF) to indicate the certainty or strength of capture in various areas. MODALL results are compared to the results from an analytical solution, a pathline analysis using MODPATH, and solute transport simulation with MT3DMS. A brief case study is also presented where MODALL is used to optimize an existing pump-and-treat system to more effectively and more efficiently contain a 5000-m long plume.     

New quantitative approaches for classifying and predicting local-scale habitats in estuaries

This study has developed quantitative approaches for firstly classifying local-scale nearshore habitats in an estuary and then predicting the habitat of any nearshore site in that system. Both approaches employ measurements for a suite of enduring environmental criteria that are biologically relevant and can be easily derived from readily available maps. While the approaches were developed for south-western Australian estuaries, with a focus here on the Swan and Peel-Harvey, they can easily be tailored to any system.