Opacifiers in Late Bronze Age glasses: the use of ToF-SIMS to identify raw ingredients and production techniques

Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) is applied to the study of four samples of opaque glass of Late Bronze Age date. The technique is uniquely capable of identifying compositional heterogeneity at a sub-micron resolution within the crystalline opacifiers dispersed through homogeneous glass matrices. It is shown that this provides crucial information on the possible raw ingredients of the opacifying inclusions used, and has the potential for highlighting regional variations in the production technology involved in creating different colours of opaque glass.     

GRAVITY AND SPATIAL STRUCTURE: THE CASE OF INTERSTATE MIGRATION IN MEXICO*

ABSTRACT The estimation of gravity models of internal (aggregate) place‐to‐place migration is plagued with endogeneity (omitted‐variable) biases if the unobserved effects of spatial structure are not accounted for. To address this econometric problem, this paper presents a more general specification of the gravity model, which allows for (bilateral) parameter heterogeneity across individual migration paths—along with (unilateral) origin‐ and destination‐specific effects. The resultant “three‐way fixed‐effects” (3FE) model is applied for an analysis of interstate migration in Mexico based on cross‐sectional data. To overcome parameter‐dimensionality problems (due to limited or incomplete information), the 3FE model is estimated using the Generalized Maximum Entropy (GME) estimator. The empirical implications of this new modeling strategy are illustrated by contrasting the 3FE‐GME estimates with those for the traditional and two‐way fixed‐effects (2FE) models. The former are far more plausible and intuitively interpretable than their traditional and 2FE counterparts, with parameter estimates changing in expected directions. The (average) effect of the migrant stock is markedly smaller than usually estimated, providing a more realistic measure of network‐induced migration. Migration outflows from centrally located origins have significantly steeper distance decay. Path‐specific distance effects exhibit directional asymmetries and spatial similarities.     

INTRODUCTION: PROCESSES OF CHANGE IN URBAN SYSTEMS*

ABSTRACT The twenty‐first century will be one of intensified urbanization, on a scale never before experienced. How do urban systems and individual cities change and develop? The social sciences have many different approaches to analyzing the economic, social, and spatial dimensions of urban change. We inventory some of these approaches and their implications for public policy toward cities, urban change, and economic development.     

Network Location and Policy‐Oriented Behavior: An Analysis of Two‐Mode Networks of Coauthored Documents Concerning Climate Change in the Great Lakes Region*,†

This study explores how a scientist's location in science‐based policy networks can affect her policy‐oriented behaviors. In particular, we hypothesize that those scientists who fill structural holes in their networks will be more likely than others to engage in policy‐oriented behaviors. The network data are defined by scientists' coauthorship on policy documents regarding climate change in the Great Lakes. We employ a two‐mode network analysis to identify clusters of scientists who coauthored similar documents, and relative to those clusters, we identify those who fill structural holes by bridging between clusters. We find that those scientists who bridged between clusters were more likely to engage in policy‐oriented behaviors of policy advocacy and advising than were others in the network. This is an example of a link between network location and policy‐oriented behavior indicative of the broader phenomenon of how individuals exert agency, given structural constraints.     

Linking Land and Navy: archaeological investigations at the site of the Woolwich Royal Dockyard,south‐eastern England

This paper outlines the archaeological evidence found at the demolished Royal Naval Dockyard at Woolwich for the development and construction of dockyard structures of the 18th to early‐19th centuries. This is set within the framework provided by historic, documentary, map and historic‐model evidence. The results of earlier excavations at the same facility are also reviewed. The themes covered include; the interplay of ‘carpentry’ versus ‘shipwrightry’ in dockyard construction, aspects of naval timber‐supply and landscape, the recycling of ships' timbers, dockyard craft specialisation and changing relative sea‐levels. © 2011 Pre‐Construct Archaeology Limited