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Patrick Schmidt Tabea J. Koch Christoph Berthold Frieder Lauxmann Klaus G. Nickel 《Archaeometry》2023,65(2):409-422
Birch tar was the first adhesive produced by humans. Its study has consequences for our understanding of human evolution and the development of specialised craftsmanship. One of the better-documented birch tar making methods is the ‘double-pot’ technique, where two containers are used, one containing bark, the other collecting the tar. Birch tar made with double-pots has low viscosity and bad adhesive properties. To obtain a usable adhesive, it must be reduced in volume by cooking. We investigate the evolution of tar’s mechanical properties during cooking. We use lap-shear tests to investigate strength, stiffness and failure behaviour. We found that tar must be cooked for 90 min to acquire adhesive properties. When cooked for longer, strength and stiffness increase over a 30 min lasting time span. Cooking for even longer, beyond this 30 min window, produced a substance that could no longer be used as an adhesive. The implications are that tar cooking requires a high level of skill because specific signs indicating the desired properties must be recognised during the process. Tar cooking constitutes a supplementary investment in time and resources and appears to be associated with a certain degree of risk. 相似文献
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This paper outlines the policy decision to implement a performance incentive program in a large social services agency. Specifically, it describes the evolution of services to homeless people in New York City, including the creation of the New York City Department of Homeless Services, the privatization of a majority of the shelter system, and the redefinition of the role of government in the provision of homeless services. It explains how performance measurement is an integral part of this evolution, and the numerous challenges that this initiative has presented to management of the Department. 相似文献
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Patrick Chabal 《International affairs》2000,76(4):825-832
This article seeks to uncover the extent to which our ways of understanding contemporary Africa are influenced by our national (historical, cultural, political, intellectual) traditions through an examination of the influential French journal Politique Africaine , whose twentieth anniversary falls this year. In a wide-ranging review article that discusses in detail the 1999 issues of Politique Africaine but is informed by a consideration of the 'deep history' of that journal, the author argues that the French Africanist political scientists whose views appear in the journal are somewhat reluctant to open up to some of the new analysis of Africa available today. 相似文献
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P. Patrick 《International Journal of Osteoarchaeology》2006,16(4):347-354
This paper examines one of a number of weapon‐injury victims from the cemetery at Church End in Cherry Hinton, Cambridge (Hertfordshire Archaeological Trust/Archaeological Solutions site HAT358), which was in use from the late Anglo‐Saxon period until after the Norman Conquest. Drawing on precedents set by forensic studies, palaeopathology and more traditional spatial cemetery analysis, assertions are made about the nature of the attack and its context. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Patrick Armstrong 《Geographical Research》2001,39(2):249-252
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