pXRF method development for elemental analysis of archaeological soil

Portable X-ray fluorescence (pXRF) is now widely used for detecting the elemental composition of a material. Elemental analysis can enhance archaeological interpretations, such as mapping, preservation analysis and identifying anthropogenic activities. However, validated and reproducible protocols for analysing archaeological soil are still required. The elemental concentrations detected with three sets of preparation methods were compared: in-situ (no preparation), in-field (analysing through plastic bags) and ex-situ analysis (laboratory-based preparation). Influential factors were also investigated: calibration parameter, moisture, homogeneity, sieve size and soil type. In-field analysis attempted to improve reliability without offsite processing, but instead substantially reduced elemental concentrations and skewed the proportional distributions. Ex-situ analysis significantly increased elemental concentrations and reduced variation. Proportional distribution was different between the three methods, but unchanged following homogenizing and sieving. These comparisons demonstrated that ex-situ analysis maximizes detection and ensures consistent samples.     

Specification of the World City Network

World cities are generally deemed to form an urban system or city network but these are never explicitly specified in the literature. In this paper the world city network is identified as an unusual form of network with three levels of structure: cities as the nodes, the world economy as the supranodal network level, and advanced producer service firms forming a critical subnodal level. The latter create an interlocking network through their global location strategies for placing offices. Hence, it is the advanced producer service firms operating through cities who are the prime actors in world city network formation. This process is formally specified in terms of four intercity relational matrices—elemental, proportional, distance, and asymmetric. Through this specification it becomes possible to apply standard techniques of network analysis to world cities for the first time. In a short conclusion the relevance of this world city network specification for both theory and policy‐practice is briefly discussed.     

The Impact of Agglomeration Economies on Estimated Demand Thresholds: An Extension of Wensley and Stabler

Central place theory predicts that geographic markets located in rural areas have lower demand thresholds, and, therefore, a higher frequency of business establishments relative to areas that are more proximate to urban centers, other things equal. Wensley and Stabler (1998) confirm this prediction using data on the location and frequency of business activities in rural Saskatchewan. We demonstrate that this relationship may not always hold true depending on the existence and magnitude of agglomeration economies. If average cost differences associated with being located in an urbanized area are sufficiently large, then the relationship between urban proximity and number of establishments may be reversed. We provide evidence of this reversal using 1996 cross-sectional data on hospital services in Texas.