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Regional Dynamics (regional + dynamics)
Selected AbstractsRegional dynamics of the fMRI-BOLD signal response to hypoxia-hypercapnia in the rat brainJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2003Sridhar S. Kannurpatti PhD Abstract Purpose To examine the regional blood oxygenation level-dependent (BOLD) signal response to rapid changes in arterial oxygen tension. Materials and Methods Functional MR imaging (fMRI) was carried out in five male Sprague-Dawley rats anesthetized with Sodium Pentobarbital. Rats were subjected to different durations of apnea as a rapid, graded, and reversible hypoxic-hypercapnic stimulus. Dynamics of the BOLD signal response were studied on a pixel-by-pixel basis in the cerebral cortex, hippocampus, third ventricle, and thalamus in the rat brain. Results Apnea induced a BOLD signal drop in all the brain regions studied, the magnitude of which increased with longer durations of the stimulus. The signal recovered to preapnic baseline levels after resumption of normal ventilation. Regional variation in the BOLD signal dynamics was observed with the magnitude of the BOLD signal change in the hippocampus being the least, followed by a relatively larger change in the thalamus, cerebral cortex, and third ventricle. The time (t0) for the signal change after the onset of the stimulus was estimated for every pixel. Time delay maps generated show the highest onset time values in the hippocampus followed by the thalamus, cerebral cortex, and third ventricle. Conclusion The regional dynamics of the BOLD signal in the brain in response to apnea may vary depending on the rate of oxygen metabolism in addition to cerebral blood flow (CBF). J. Magn. Reson. Imaging 2003;17:641,647. © 2003 Wiley-Liss, Inc. [source] The Political Ecology of Transition in Cambodia 1989,1999: War, Peace and Forest ExploitationDEVELOPMENT AND CHANGE, Issue 4 2000Philippe Le Billon Over the last decade, forests have played an important role in the transition from war to peace in Cambodia. Forest exploitation financed the continuation of war beyond the Cold War and regional dynamics, yet it also stimulated co-operation between conflicting parties. Timber represented a key stake in the rapacious transition from the (benign) socialism of the post-Khmer Rouge period to (exclusionary) capitalism, thereby becoming the most politicized resource of a reconstruction process that has failed to be either as green or as democratic as the international community had hoped. This article explores the social networks and power politics shaping forest exploitation, with the aim of casting light on the politics of transition. It also scrutinizes the unintended consequences of the international community's discourse of democracy, good governance, and sustainable development on forest access rights. The commodification of Cambodian forests is interpreted as a process of transforming nature into money through a political ecology of transition that legitimates an exclusionary form of capitalism. [source] Temporal dynamics and nestedness of an oceanic island bird faunaGLOBAL ECOLOGY, Issue 4 2006Ermias T. Azeria ABSTRACT Aim, To examine temporal variation in nestedness and whether nestedness patterns predict colonization, extinction and turnover across islands and species. Location, Dahlak Archipelago, Red Sea. Method, The distributions of land birds on 17 islands were recorded in two periods 30 years apart. Species and islands were reordered in the Nestedness Temperature Calculator, software for assessing degrees of nestedness in communities. The occupancy probability of each cell, i.e. species,island combinations, was calculated in the nested matrix and an extinction curve (boundary line) was specified. We tested whether historical and current nested ranks of species and islands were correlated, whether there was a relationship between occupancy probability (based on the historical data) and number of extinctions or colonizations (regression analyses) and whether the boundary line could predict extinctions and colonizations (chi-square analyses). Results, Historical and current nested ranks of islands and species were correlated but changes in occupancy patterns were common, particularly among bird species with intermediate incidence. Extinction and turnover of species were higher for small than large islands, and colonization was negatively related to isolation. As expected, colonizations were more frequent above than below the boundary line. Probability of extinction was highest at intermediate occupancy probability, giving a quadratic relationship between extinction and occupancy probability. Species turnover was related to the historical nested ranks of islands. Colonization was related negatively while extinction and occupancy turnover were related quadratically to historical nested ranks of species. Main conclusions, Some patterns of the temporal dynamics agreed with expectations from nested patterns. However, the accuracy of the predictions may be confounded by regional dynamics and distributions of idiosyncratic, resource-limited species. It is therefore necessary to combine nestedness analysis with adequate knowledge of the causal factors and ecology of targeted species to gain insight into the temporal dynamics of assemblages and for nestedness analyses to be helpful in conservation planning. [source] Upgrading, uneven development, and jobs in the North American apparel industryGLOBAL NETWORKS, Issue 2 2003Jennifer Bair In this article we examine the developmental consequences of globalization at multiple scales, using a commodity chains framework to investigate the case of the North American apparel industry. In the first section we outline the apparel commodity chain and offer a brief typology of its lead firms. In the second section we discuss the concept of industrial upgrading and describe several main export roles in the global apparel industry. In the third section we focus on the regional dynamics resulting from the North American Free Trade Agreement (NAFTA). We contrast the Mexican experience with that of countries in the Caribbean Basin to show the impact of distinct trade policies on export-oriented development. We argue that NAFTA is creating upgrading opportunities for some Mexican firms to move from the low value-added export-oriented assembly (or maquila) model to full-package production. In the fourth section we explore the unevenness of upgrading dynamics through a comparison of two blue jeans manufacturing clusters in the United States and Mexico: El Paso and Torreon. Our conclusions about upgrading and uneven development in the North American apparel industry emphasize the importance of local, national and regional institutional contexts in shaping inter-firm networks and their development impact. [source] The Sino,Russian Partnership and U.S. Policy Toward North Korea: From Hegemony to Concert in Northeast AsiaINTERNATIONAL STUDIES QUARTERLY, Issue 3 2005David Kerr This paper presents two sets of arguments: one theoretical and one analytical. The theoretical arguments concern the relationship between regional ordering and systemic change. The paper questions the usefulness of the unipolar conception of the contemporary system arguing that the interaction of the Great Powers cannot be understood without reference to regional dynamics. Thus, a unipolar system implies considerable potential for U.S. hegemonic intervention at the regional level but in East Asia, we find an equilibrium constructed out of both material and normative forces, defined as a concert, which presents a considerable restraint on all powers, including the U.S. The paper then proceeds to examine these claims through an analysis of the foreign policies of the U.S., Russia, and China over the North Korean nuclear problem that emerged after 2002. It finds that China and Russia have substantive common interests arising from internal and external re-ordering in which they look to strategic partnerships, regional multilateralism, and systemic multipolarization as inter-locking processes. The paper finds that they have collaborated over the Korean crisis to prevent a U.S. unilateral solution but that this should not be construed as a success for an open counterhegemonic strategy as it was only under the constraining conditions of East Asian concert, including the dynamics within the U.S. alliance systems, that this collaboration was successful. Nevertheless, the paper concludes that regional multipolarity and systemic unipolarity are contradictory: a system that exhibits multipolarization at the regional level cannot be characterized as unipolar at the global level. [source] Security Theory in the "New Regionalism",INTERNATIONAL STUDIES REVIEW, Issue 2 2007Robert E. Kelly The relevance of regional security theories has grown in the wake of the Cold War. The global system has more participants,is less Eurocentric with Third World states having greater autonomy and involvement,and clearly unipolar, shifting the locus of conflict down from the global level. A new wave of regionalist scholarship has arisen in response. This review identifies this literature's central themes and suggested new variables. Its foundational and most contested challenge to international relations (IR) theory revolves around the autonomy of a regional level of analysis between the state and the globe. Accepting such autonomy, the literature broadly settles on three variables specific to regional structures. First, regional subsystems are porous. Intervention from above can overlay local dynamics. Second, proximity qualifies the security dilemma dramatically. Most states only threaten their neighbors, thus creating meaningful and distinct regional dynamics. Third, weak state-dominant regional complexes generate a shared internal security dilemma that trumps the external one. Regional organizations serve to repress shared centrifugal threats through pooled rather than ceded sovereignty. [source] Spatial variation in population growth rate and community structure affects local and regional dynamicsJOURNAL OF ANIMAL ECOLOGY, Issue 6 2008M. Kurtis Trzcinski Summary 1Theory predicting that populations with high maximum rates of increase (rmax) will be less stable, and that metapopulations with high average rmax will be less synchronous, was tested using a small protist, Bodo, that inhabits pitcher plant leaves (Sarracenia purpurea L.). The effects of predators and resources on these relationships were also determined. 2Abundance data collected for a total of 60 populations of Bodo, over a period of 3 months, at six sites in three bogs in eastern Canada, were used to test these predictions. Mosquitoes were manipulated in half the leaves partway through the season to increase the range of predation rates. 3Dynamics differed greatly among leaves and sites, but most populations exhibited one or more episodes of rapid increase followed by a population crash. Estimates of rmax obtained using a linear mixed-effects model, ranged from 1·5 to 2·7 per day. Resource levels (captured insect) and midge abundances affected rmax. 4Higher rmax was associated with greater temporal variability and lower synchrony as predicted. However, in contrast to expectations, populations with higher rmax also had lower mean abundance and were more suppressed by predators. 5This study demonstrates that the link between rmax and temporal variability is key to understanding the dynamics of populations that spend little time near equilibrium, and to predicting and interpreting the effects of community structure on the dynamics of such populations. [source] Incorporating movement into models of grey seal population dynamicsJOURNAL OF ANIMAL ECOLOGY, Issue 3 2006PHILIP J. HARRISON Summary 1One of the most difficult problems in developing spatially explicit models of population dynamics is the validation and parameterization of the movement process. We show how movement models derived from capture,recapture analysis can be improved by incorporating them into a spatially explicit metapopulation model that is fitted to a time series of abundance data. 2We applied multisite capture,recapture analysis techniques to photo-identification data collected from female grey seals at the four main breeding colonies in the North Sea between 1999 and 2001. The best-fitting movement models were then incorporated into state-space metapopulation models that explicitly accounted for demographic and observational stochasticity. 3These metapopulation models were fitted to a 20-year time series of pup production data for each colony using a Bayesian approach. The best-fitting model, based on the Akaike Information Criterion (AIC), had only a single movement parameter, whose confidence interval was 82% less than that obtained from the capture,recapture study, but there was some support for a model that included an effect of distance between colonies. 4The state-space modelling provided improved estimates of other demographic parameters. 5The incorporation of movement, and the way in which it was modelled, affected both local and regional dynamics. These differences were most evident as colonies approached their carrying capacities, suggesting that our ability to discriminate between models should improve as the length of the grey seal time series increases. [source] Effects of regional climate and small-scale habitat quality on performance in the relict species Ramonda myconiJOURNAL OF VEGETATION SCIENCE, Issue 2 2002M. Riba Bolòs et al. (1993) Abstract. The Mediterranean Basin harbours paleo-endemic species with a highly restricted and fragmented distribution. Many of them might also be of the remnant type, for which the regional dynamics depends on the persistence of extant populations. Therefore, a key issue for the long-term persistence of these species is to assess the variability and effects of ecological factors determining plant performance. We investigated the spatio-temporal variability in plant traits and ecological factors of Ramonda myconi, a preglacial relict species with remnant dynamics, in 5 populations over 4,7 yr. Ecological factors contributing to fecundity showed a high degree of between-year variability. Pre-dispersal fruit predation had a minor influence on total reproductive output, and most of the variability was found among individuals within populations and years. Spatio-temporal variability in growth and survival was rather low but significant, whereas recruitment showed important between-population variability. Among-year variability in fecundity and growth was related to climatic fluctuations on a regional scale, notably rainfall and temperature in a particular period, while the spatial variability in survival and recruitment was explained by within-population (patch) habitat quality. Although R. myconi is able to withstand repeated periods of drought, water availability seems to be the most important factor affecting plant performance in all the study populations. These findings suggest that the long-term persistence of species showing remnant population dynamics in habitats under the influence of Mediterranean climate might be threatened by increased aridity as a result of climate change. [source] How Can the United States Take the Initiative in the Current North Korean Nuclear Crisis?PACIFIC FOCUS, Issue 2 2005Jin H. Pak On September 19, 2005, the last day of the fourth round of six-party talks, a deal was announced in which North Korea pledged to end its nuclear program in return for a number of concessions. Within 24 hours of that announcement, North Korea clarified its position by stating that the United States "should not even dream" it would dismantle its nuclear weapons until it receives a light-water nuclear reactor. Despite four rounds of six-party talks over a three year period, it seems that almost no real progress has been made, except for North Korea; US intelligence officials estimate that North Korea could have made as many as 8 or 9 nuclear weapons already. So it seems North Korea has cleverly increased its bargaining position vis-à-vis the United States. As lengthy negotiations over the provision of a Light Water Reactor (LWR) will undoubtedly ensue, it can use that time to steadily increase its nuclear deterrent. Why did the United States agree to this sub-optimal outcome? Why was it so difficult for the United States to exert more influence on North Korea and the other countries in the six-party talks? The answer to these questions lies in the changing trends affecting Northeast Asian security dynamics. For various reasons that this article will explain, these trends affect the ability of the United States to take the initiative in the ongoing North Korean nuclear crisis. As long as the United States fails to account for various changes in Northeast Asian regional dynamics, its strategy will to deter North Korea from continuing its nuclear program will not succeed. [source] China and Northeast Asia: A Complex Equation for ,Peaceful Rise'POLITICS, Issue 3 2007Jae Ho Chung This article tackles the question: has China become more proactive and willing to resolve regional problems unilaterally, bilaterally or multilaterally? It suggests that, while China has clearly become more proactive in facilitating regional stability and co-operation, it still has to overcome certain perceptual hurdles and constrain its impulse to be the ,centre' of the world. Consisting of three sections, this article first discusses the nexus between post-Mao China's ,new' diplomacy and Beijing's proactive posture towards Asia and notes the troublesome nature of the regional dynamics in Northeast Asia. It then explores three case studies in which China's activism has varied in resolving intricate regional and inter-state problems: namely, Sino,Japanese discord, the Koguryo controversy between South Korea and China and the North Korean nuclear conundrum. The final section offers some concluding observations regarding China's diplomacy towards Northeast Asia. [source] | ||||||||||||||||||||||