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Having been adopted by legislatures in over a dozen states, postsecondary merit aid programs are largely concentrated in the southeastern United States. The observed clustering pattern seems to support previous evidence that policies spread between proximate states, a phenomenon referred to by political scientists as policy diffusion. Often, however, policy diffusion is not complete, and one or more states in a region fail to adopt. By interviewing policymakers throughout the southeastern United States—including actors in the three states in the region without merit aid—the study addresses the following question: Why do diffusion pressures lead to adoption in some states but not in others? Studying state “hold‐outs” promises not only to uncover the reasons for failed legislation in specific state contexts but also to better our understanding of the limits of diffusion theory. 相似文献
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Methods of soil P analysis in archaeology 总被引:2,自引:0,他引:2
Phosphorus (P) is unique among the elements in being a sensitive and persistent indicator of human activity. It has long been of interest to archaeologists because of its potential to inform them about the presence of past human occupation and to offer clues regarding the type and intensity of human activity. A wide variety of methods have been developed in both soil science and in archaeology to extract and measure soil P, resulting in a tremendous amount of data and a wide array of interpretations, but also considerable confusion over appropriateness of methods and terminology. The primary purpose of this paper is to address these issues by clarifying soil P analyses. Anthropogenic additions of phosphorus to the soil come from human refuse and waste, burials, the products of animal husbandry in barns, pens, and on livestock paths, or intentional enrichment from soil fertilizer. Once added to the soil, phosphorus in its common form as phosphate is stable and generally immobile in soils. Soil P comes in many forms, organized for the purposes of this paper on the basis of extraction and measurement procedures as (1) extraction for available P (Pav); (2) portable field techniques (the spot test or ring test); (3) chemical digestion of a soil sample for total P (Ptot); (4) extractions of inorganic P (Pin) for fractionation studies and extractions to look at individual compounds of P; (5) measurements of organic P (Porg); and (6) extractions for total elemental analysis. To compare the suitability of various extractants as the “best” indicator of human input and activity we subjected samples from three very different archaeological sites (Lubbock Lake, TX; Hulburt Creek, IA; British Camp, WA) to four methods of soil P extraction: perchloric acid digestion (Ptot), sulfuric–nitric acid extraction Ptot), hydrochloric acid extraction after ignition (Pin), and citric acid extraction (Pav). Further, methods of measurement were compared via colorimetry vs. Inductively Coupled Plasma (ICP) spectrometry, and the two methods of supposed “total P” were both measured via ICP. In general, the stronger extractants yielded more soil P, but the result are not clear-cut. Likely variables include the intensity of occupation, nature of the parent material, and postdepositional weathering (e.g., the addition of dust). 相似文献
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William T. Tow 《Australian Journal of International Affairs》2007,61(2):153-155
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Schneider WH 《Journal of the history of medicine and allied sciences》2003,58(2):187-224
This article examines the introduction of blood transfusion into general practice from the end of the First World War to the Second World War. Developments during most of this period were not the result of new discoveries but rather the spread of ideas and the establishment of donor organizations to secure an adequate blood supply. The identification, testing, and organization of potential donors were done in a wide variety of settings that reflected differences in political and cultural experiences. At the end of the 1930s, with war approaching, the resolution of problems with storage of blood and the discovery of new techniques for separating and storing plasma dramatically changed transfusion practice. Thus, the innovations of the Second World War were very much based on the development of broad donor organizations plus the new technical discoveries that had occurred during the interwar period. 相似文献
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Nearly all segregation measures use some form of administrative unit (usually tracts in the United States) as the base for the calculation of segregation indices, and most of the commonly used measures are aspatial. The spatial measures that have been proposed are often not easily computed, although there have been significant advances in the past decade. We provide a measure that is individually based (either persons or very small administrative units) and a technique for constructing neighborhoods that does not require administrative units. We show that the spatial distribution of different population groups within an urban area can be efficiently analyzed with segregation measures that use population count‐based definitions of neighborhood scale. We provide a variant of a k‐nearest neighbor approach and a statistic spatial isolation and a methodology (EquiPop) to map, graph, and evaluate the likelihood of individuals meeting other similar race individuals or of meeting individuals of a different ethnicity. The usefulness of this approach is demonstrated in an application of the method to data for Los Angeles and three metropolitan areas in Sweden. This comparative approach is important as we wish to show how the technique can be used across different cultural contexts. The analysis shows how the scale (very small neighborhoods, larger communities, or cities) influences the segregation outcomes. Even if microscale segregation is strong, there may still be much more mixing at macroscales. 相似文献