On modeling of chemical stimulation of an enhanced geothermal system using a high pH solution with chelating agent

Dissolution of silica and calcite in the presence of a chelating agent (NTA) at a high pH was successfully demonstrated in laboratory experiments using a high-temperature flow reactor. (Note that the term 'silica' used here includes amorphous silica, quartz, and silicate glass bead.) The mineral dissolution and associated porosity enhancement in the experiments were reproduced by reactive transport modeling using TOUGHREACT. The chemical stimulation method was applied by numerical modeling to a field geothermal injection well system to investigate its effectiveness. Parameters applicable to the quartz monzodiorite unit at the Enhanced Geothermal Systems site at Desert Peak (Nevada) were used. Results indicate that the injection of a high pH chelating solution results in dissolution of both calcite and plagioclase, while avoiding precipitation of calcite at high temperature conditions. Consequently, reservoir porosity and permeability can be enhanced especially near the injection well. Injection at a lower temperature of 120°C (temperature is over 160°C in the base-case) results in a porosity increase that is smaller close to the injection point, but extends to a larger radial distance. A slower kinetic rate results in less aggressive mineral dissolution close to the injection point and larger extent along the flow path, which is favorable for chemical stimulation.     

The influence of poorly interconnected fault zone flow paths on spring geochemistry

Thermal springs commonly occur along faults because of the enhanced vertical permeability afforded by fracture zones. Field and laboratory studies of fault zone materials document substantial heterogeneities in fracture permeabilities. Modeling and field studies of springs suggest that spatial variations in permeability strongly influence spring locations, discharge rates and temperatures. The impact of heterogeneous permeability on spring geochemistry, however, is poorly documented. We present stable isotope and water chemistry data from a series of closely spaced thermal springs associated with the Hayward Fault, California. We suggest that substantial spatial variations observed in δ¹⁸O and chloride values reflect subsurface fluid transport through a poorly connected fracture network in which mixing of subsurface waters remains limited. Our measurements provide insight into the effect of fracture zone heterogeneities on spring geochemistry, offer an additional tool to intuit the nature of tectonically induced changes in fault zone plumbing, and highlight the need to consider local variations when characterizing fracture zone fluid geochemistry from spring systems with multiple discharge sites.     

Radar and Air Defence in the 1930s

The article sets out to demonstrate that radar played a central,but hitherto unrecognized, role in the formation of Britishair policy during the 1930s. It is generally conceived thatthe secret of radar was stumbled across, as if by accident,in early 1935, and was then employed to devastating effect inthe Battle of Britain. The article, however, shows that thedesire for an effective instrument for air defence had gestatedduring the First World Wart—when Britain sought to fightoff the Zeppelin and Gotha bombing raids—and the searchcontinued throughout the 1920s and early 1930s. Moreover, theprinciple of radar had been known since 1904, but scientificbackwardness precluded practical progress. There is detailedexamination of the intricate political manoeuvring by PrimeMinister Stanley Baldwin and others which accompanied the adoptionof radar as Britain's primary line of defence against the Luftwaffein preference to the increasingly obsolete doctrine of bomberdeterrence. In conclusion, radar was deliberately developed,and consciously conceived of, as a device that would be slottedinto a proved framework of observation and organization constructedon top of Britain's First World War air defence system.     

Contexts of interpretation: assessing immigrant reception in Richmond, Canada

This article examines the responses of established residents to contemporary physical and social changes in Richmond, British Columbia, a Vancouver suburb that has received a considerable number of ethnic-Chinese immigrants over the past decade. In the metropolitan Vancouver context, recent considerations of immigrant reception at the neighbourhood level have focused on the critical reactions of 'white', European-origin residents in upper-middle class areas to local immigrant settlement and housing stock transformations. These studies have given rise to conflicting interpretations of the relationship between immigration and neighbourhood landscape change, the motivations behind resident protest and, in particular, the definition of their responses as racist. Drawing from extended interviews with fifty-four long-term Richmond residents, I attempt to provide a broader account of immigrant reception as a supplement to works that have revolved around housing issues and 'white' resistance. I also critique the way that the term racism has been used to describe resident reactions to immigration-related changes, calling for researchers to be more reflexive and explicit in their application of the concept.     

Imaging Evaluation of Skull Trepanation Using Radiography and CT

Cranial surgery as practised by the prehistoric and present-day traditional medicine man is the oldest known and one of the highest surgical achievements in the history of medicine. This study examines morbidity and mortality of this ancient surgical procedure by re-examining and reviewing reports of 71 completely trepanned skulls from pre-Columbian Peru by three techniques: gross visual observation and palpation; radiography; and CT. The specimens are located in the San Diego Museum of Man and are part of the Hrdlicka collection. Clear distinction can be made by visual observation between skulls with bone regeneration and those without; that is, between patients who survived long enough to allow bone healing and those who died immediately or within a few days of the operation. 64.8 per cent of skulls had complete healing, 12.7 per cent had partial healing and 22.5 per cent had no evidence of healing. Thus, a post-operative survival rate of 77.5 per cent is noted by gross examination. The meaning of completely trepanned skulls with no evidence of healing is questionable, however, some unhealed skulls may represent post-mortem trepanation, suggesting a lower surgical mortality. Both radiography and CT scan demonstrate with considerable accuracy the presence or absence of new bone formation on trepanned skulls. One skull demonstrated evidence of partial bone healing by CT and radiography but not by our gross examination or by that of some anthropologists. Evidence of osteomyelitis was illustrated by CT scan but not by radiography.     

Constructing gender,constructing the urban: A review of Anglo-American feminist urban geography

This essay explores the changing shape of Anglo-American feminist urban geography, through a discussion of material published in Gender, Place and Culture and elsewhere over the past decade. We contextualize this discussion in relation to the development of feminist urban studies since the 1970s, showing its enduring commitment to work across traditional analytical divides that obfuscate crucial aspects of the mutual constitution of gender and the urban. Focusing on two thematic areas--affective experiences of urban space, and the making of urban public spaces--we examine how this commitment is expressed in recent contributions to feminist urban geography. Both bodies of work successfully challenge a divide between scholarship that focuses on how cities constrain, disadvantage and oppress women, and scholarship that focuses on how cities liberate women. However, we are disturbed by a seeming bifurcation between work concerned with issues of recognition and work focusing on issues of redistribution, with the former being well represented in Gender, Place and Culture and the latter more likely to be aired in 'mainstream' journals. We conclude by reflecting on our lack of perspective on the trajectories of feminist urban geography outside of the Anglo-American context and ask whether the boundaries within which our review has been conducted are themselves gendered.