Studies in Urban Ecology: the First Wave of Biological Invasion by Pistacia chinensis in Armidale,New South Wales,Australia

Biological invasions by deliberately introduced organisms seriously compromise the integrity of ecosystems, but their early stages have seldom been documented, especially in urban contexts. Since the 1940s, the small Asian tree Pistacia chinensis has been widely planted in streets and gardens in Armidale, New South Wales, Australia, where it makes a major contribution to the autumn colours that are exploited to promote the city. Numerous wild plants are now becoming established in and near Armidale. This ongoing biological invasion may have been accelerated by the large size of the initial (planted) population, and by the presence of efficient avian seed dispersers. It is now at the stage of the first wild generation reaching reproductive maturity. While it is probably still possible to halt the invasion, various human factors appear to make this an unlikely prospect.     

Experimental study of aqueous fluid infiltration into quartzite: implications for the kinetics of fluid redistribution and grain growth driven by interfacial energy reduction

To investigate the kinetics of interfacial energy‐driven fluid infiltration, experiments were carried out in a quartzite–water system at 621–925°C and 0.8 GPa. Infiltration couples were made by juxtaposing presynthesized dry quartzite cylinders and fluid reservoirs. The infiltration process was confirmed by the presence of pores at the quartzite grain edges. As predicted from theoretical considerations and previous experiments, wetting fluids such as pure water and NaCl aqueous solution infiltrated into quartzite, whereas nonwetting CO₂‐rich fluids did not. Newly precipitated quartz layers at the surfaces of the infiltrated sample proved that infiltration took place by a dissolution–precipitation mechanism. The enhancement of grain growth by fluid infiltration was observed over the entire range of experimental temperatures. The fluid fraction, gauged by the porosity of the run products, increases at the infiltration front and then decreases towards the fluid reservoir to form a high‐porosity zone with a maximum porosity of 2.3–2.9%. As infiltration proceeds, the high‐porosity zone advances like a travelling wave. This porosity wave is probably caused by a grain curvature gradient resulting from preferential grain growth in the infiltrated part of the quartzite, perhaps combined with other factors. The infiltration kinetics were modelled with a steady‐state diffusion model over the high‐porosity zone. The solubility difference between dissolving and precipitating grains was deduced to be 2 × 10^?2?3 × 10^?1 wt %. The experimentally obtained infiltration rate of aqueous fluid in the steady‐state diffusion regime (2 ± 0.5 × 10^?8 m sec^?1 at 823°C) is much faster than the estimated metamorphic fluid flux rates, so that interfacial energy‐driven fluid redistribution in quartz‐rich layers could significantly contribute to the fluid flux in high‐grade metamorphism, at least over a short distance. Cathodoluminescence observations of the run products revealed that the grain growth of quartzite in the presence of fluid proceeds extensively, which would promote the chemical equilibration between fluid and rock more effectively than would volume diffusion in quartz crystals.     

Geographic aspects of genocide: a comparison of Bosnia and Rwanda

The study of genocide requires a geographic approach that looks at how genocidal actions are purposefully planned to target specific groups and areas, methodically implemented through expulsions and murder, and politically intertwined with popular aspirations of territorial nationalism. A geographic focus is used here to discuss the concept of genocide, its recurrence in the twentieth century, its formulation under international law, and its eruption in Bosnia and Rwanda. In this comparative approach, geography-linked concepts such as Lebensraum , territorial nationalism, forced migration, and ethnic cleansing are used to explain the production of genocide and its consequences.     

Development and the Role of Microcredit

Microcredit is a concept that has gained widespread acceptance by international development agencies and major donors. It is viewed as a way to correct both governmental and market failure in Sub-Saharan Africa. Many view microcredit as a method for linking the formal and informal sectors of African economies to increase the reach of the formal sector. Extending the reach of the formal economy through microcredit is possible, and desirable, depending on macroeconomic reforms, respect for traditional financing relationships, and local control of institutions. However, very little has been done to determine the extent to which microcredit programs actually increase economic well-being. The model program, Grameen Bank of Bangladesh, has been studied and evaluated, but replications may not be inherently successful. The literature accepts that microcredit will increase economic well-being, if programs are correctly designed. Program design issues cannot be resolved, however, until economic well-being is measured and associated with specific designs.