Most scholars of tribal organization among the Bedouin of the eastern Arab world utilize a two-dimensional, hierarchical model of Bedouin kinship that represents only relations of descent and affinity. This model resembles a genealogy and shows how small descent units are enclosed by larger ones. It implies that tribes grow in size only through biological reproduction. Such a representation of the Bedouin tribe fails to distinguish politically central lineages from politically peripheral lineages and also ignores the processes through which foreign lineages become “attached” as clients to politically powerful, central lineages. To correct and supplement this genealogical model, the author presents a concentric model of Bedouin tribes that adds a “central/peripheral” distinction. This model also includes relations of political “attachment” that can affect the internal morphology and growth of Bedouin tribes in ways that are comparable to the effects of affinal and suckling kinship relations on internal organization. The proposed concentric model thus allows us to represent historical change more accurately and also brings us closer to Bedouin concepts of tribal organization.

Kinship is an important dimension of politics throughout the Middle East and, specifically, in Jordan. At the level of face-to-face negotiations, three kinds of kinship (common descent, affinity, ritual kinship) are invoked in Jordan to garner support from an actor’s kin and create political ties. At the level of large-scale organizations – such as tribes – appeals are made to kinship norms to mobilize members of each organization and enhance group solidarity. At the macroscopic level of national politics, rhetoric about the “national family” is used to try to pacify groups who have lost political battles or who are politically marginal to the decision-making process. Analysis of politics at all three levels can be improved by paying careful attention to kinship.

Oceanic motion outside thin boundary layers is primarily a mixture of quasi-geostrophic flow and internal waves with either near-inertial frequencies or the frequency of the semidiurnal lunar tide. This dissertation seeks a deeper understanding of waves and flow through reduced models that isolate their nonlinear and coupled evolution from the Boussinesq equations. Three physical-space models are developed: an equation that describes quasi-geostrophic evolution in an arbitrary and prescribed field of hydrostatic internal waves; a three-component model that couples quasi-geostrophic flow to both near-inertial waves and the near-inertial second harmonic; and a model for the slow evolution of hydrostatic internal tides in quasi-geostrophic flow of near-arbitrary scale. This slow internal tide equation opens the path to a coupled model for the energetic interaction of quasi-geostrophic flow and oceanic internal tides.

Four results emerge. First, the wave-averaged quasi-geostrophic equation reveals that finite-amplitude waves give rise to a mean flow that advects quasi-geostrophic potential vorticity. Second is the definition of a new material invariant: Available Potential Vorticity, or APV. APV isolates the part of Ertel potential vorticity available for balanced-flow evolution in Eulerian frames and proves necessary in the separating waves and quasi-geostrophic flow. The third result, hashed out for near-inertial waves and quasi-geostrophic flow, is that wave-flow interaction leads to energy exchange even under conditions of weak nonlinearity. For storm-forced oceanic near-inertial waves the interaction often energizes waves at the expense of flow. We call this extraction of balanced quasi-geostrophic energy `stimulated generation' since it requires externally-forced rather than spontaneously-generated waves. The fourth result is that quasi-geostrophic flow can encourage or `catalyze' a nonlinear interaction between a near-inertial wave field and its second harmonic that transfers energy to the small near-inertial vertical scales of wave breaking and mixing.

We derive a closed master equation for an individual-based population model in continuous space and time. The model and master equation include Brownian motion, reproduction via binary fission, and an interaction-dependent death rate moderated by a competition kernel. Using simulations we compare this individual-based model with the simplest approximation, the spatial logistic equation. In the limit of strong diffusion the spatial logistic equation is a good approximation to the model. However, in the limit of weak diffusion the spatial logistic equation is inaccurate because of spontaneous clustering driven by reproduction. The weak-diffusion limit can be partially analyzed using an exact solution of the master equation applicable to a competition kernel with infinite range. This analysis shows that in the case of a top-hat kernel, reducing the diffusion can increase the total population. For a Gaussian kernel, reduced diffusion invariably reduces the total population. These theoretical results are confirmed by simulation. (c) 2006 Elsevier Inc. All rights reserved.

Nanotechnology innovations create an exciting focus for research in regenerative medicine. Nanomaterials, which form the basis of one of the booming fields of nanotechnology, have tremendous potential for tissue engineering. Many common debilitating and life-threatening diseases arise from the loss or dysfunction of specific tissue types in the body, such as peripheral nerve damages, spinal cord injuries and vascular diseases. To date, peripheral nerve, spinal cord, and vascular regeneration remains a significant challenge in regenerative medicine. The use of electrospinning to generate functional nanofibrous scaffolds for tissue regeneration is particularly exciting, as the structure and morphology of electrospun scaffolds can be manipulated to resemble that of extracellular matrix (ECM), therefore creating a more "familiar" environment for the cells. Synthetic polymer scaffolds composed of either homopolymers or copolymers are biocompatible, have configurable mechanical properties, and can be easily incorporated with bioactive molecules and stem cells to promote nerve, spinal cord, and vascular repair. Aligned nanofibers in the scaffold can enhance regeneration in damaged nerves, accelerate axon growth and angiogenesis in spinal cord injuries, and organize cell alignment and stimulate cell organization in vascular remodeling. In vivo studies demonstrate that bi-layer aligned nanofibrous scaffolds have considerable therapeutic effects for tissue regeneration. In addition, nanofibrous scaffolds offer a valuable platform for drug delivery for spinal cord regeneration. Our studies integrate life science and engineering disciplines to create new generations of prosthetic and medical implants with nanotechnology innovations, intended to benefit patient healthcare in the long run.

Abnormal vascular remodeling mediated by inflammatory cells has been identified as a key pathologic component of various vascular diseases, including abdominal aortic aneurysms, brain arteriovenous malformations and atherosclerosis. Based on findings from observational studies that analysed human intracranial aneurysms and experimental studies that utilized animal models, an emerging concept suggests that a key component of the pathophysiology of intracranial aneurysms is sustained abnormal vascular remodeling coupled with inflammation. This concept may provide a new treatment strategy to utilize agents to inhibit inflammation or cytokines produced by inflammatory cells such as matrix metalloproteinases. Such an approach would aim to stabilize these vascular lesions and prevent future expansion or rupture.