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91.
Concurrent to the surge of U.S. forces in Iraq between 2006 and 2008, Sunni tribesmen in the U.S. Marine‐controlled western Anbar province of Iraq experienced an “awakening” movement, which led them to side with U.S. and coalition forces. The Sunni Awakening demonstrates that individuals will often realign because of betrayal and opportunities for advancement. It also demonstrates that individual motives can have macrolevel social consequences. Complexity theory suggests that political factions will realign based on individual considerations that then develop into macrolevel movements. Complexity theory also combines both agency (in terms of microbehaviors) and structure (in terms of initial conditions). An important concept within the complexity literature is the idea of “critical mass.” Theories of self‐organization suggest that individual considerations aggregate to a point of critical mass to become macrolevel movements. In the case of Iraq, you had individuals who decided as individuals to align with the Americans, but the macrolevel Awakening movement did not gain momentum until enough individuals had joined the movement. This pattern suggests that complexity theory can be used as a framework for understanding how critical mass is achieved in realignment.  相似文献   
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This article examines the role of Iran in Yemen within the context of Arab‐Iranian relations. It also examines the debate on the involvement of Iran in the ongoing political developments in Iraq, Lebanon, and Syria. The article focuses on the Houthi Movement in Yemen, its origin, growth and political expansion. It also investigates its relations with Iran and its allies in the region, and discusses other factors that strengthened its political image in Yemen. The article also provides an early assessment of the implication of the Decisive Storm military led by Saudi Arabia.  相似文献   
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This paper extends the utility maximization model of migration by introducing income and unemployment‐related uncertainties as determinants of utility, and analyzes the effects of the informational advantages of migrants. The paper maintains that migration would expand an individual's economic choices and opportunities and allow diversification. Consequently, diversification advantages influence the location decisions of migrants, an effect captured by the correlation of incomes at the origin and potential destinations. We use the discrete choice model based on random utility maximization as the framework for our empirical investigation of migration from the United States rural to urban counties. This paper takes advantage of an equivalent relation between the conditional logit model and Poisson regression to study the migration decisions using aggregate data among a large set of spatial alternatives. The results show that the diversification concerns have significant effects on location decisions of the rural‐urban migrants in the United States.  相似文献   
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Colonial scleractinian corals were sampled from three levels within a Miocene marine unit of the Bakhtiari succession, Zagros Basin, central-western Iran. The first two coral-bearing intervals, A and B, contain small-scale scattered colonies and show a poor coral diversity, whereas the third, consisting of a strongly lithified limestone package, reflects a well-developed biostromal framework with higher coral skeletal volume within the Bakhtiari succession. The Bakhtiari succession coral assemblages are characterized by Porites sp. cf. P. maigensis, Porites sp. cf. P. mancietensis, Porites sp. cf. P. collegniana, Tarbellastraea reussiana, Favia sp., Montastrea sp. cf. P. tchihatcheffi, Favites sp. cf. P. neugeboreni, Favites sp. cf. P. neuvillei, Agathiphyllia sp. and Acropora sp. Sedimentological and palaeontological data indicate that the depositional environment is consistent with a mixed carbonate–siliciclastic ramp that was gently deepening basinwards from the shoreline. The hemispherical and massive growth forms of colonies and sparse branching forms dominated the well-illuminated euphotic zone. Abundant domestone and dense pillarstone coral growth fabrics interdigitating with coarse-grained terrigenous sediments developed in the shallow inner ramp environment. Branching forms and meandroid branching colonies together with some massive forms mostly inhabited the low-energy conditions of the lower euphotic to oligophotic zones of the middle ramp. In the middle parts of the mixed carbonate–siliciclastic ramp, sparse pillarstone together with domestone comprises a mixstone coral growth fabric. Fluctuations in nutrient and clastic sediment input, salinity and the growth of red algae likely terminated coral growth.  相似文献   
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