The number of co-flowering species, floral density and floral trait diversity can be major determinants of pollinator-mediated plant–plant interactions in a community. However, evaluation of how each one of these co-flowering components affects the pollination success of a single focal plant species, and how these effects vary at different spatial scales, is lacking. Here, we evaluated the effects of functional diversity (flower morphology and colour), taxonomic diversity (reflecting potential sampling effects) and flower density (conspecific and heterospecific), on the pollinator environment (i.e. visitation rate and pollinator diversity) and pollination success (i.e. pollen load size and number of pollen tubes per style) of Cakile edentula (Brassicaceae). We applied structural equation models (SEMs) at the floral-neighbourhood (plot level) and community-wide scales to uncover the factors that mediate co-flowering community effects on C. edentula pollination success. We found that co-flowering community effects at the community level are more important than fine-scale floral-neighbourhood differences in mediating plant pollination success in our study species. Increasing plant functional diversity decreased pollinator visitation rate but increased the diversity of pollinator functional groups visiting C. edentula flowers. Taxonomic diversity negatively affected pollinator diversity suggesting that other unmeasured floral traits may be relevant or that single-species effects (sampling effects) may be important. Overall, our results suggest that functional floral trait diversity in a community may be the most important factor influencing pollination success of species in a community. We also found evidence for intra- and interspecific pollinator competition mediated by flower density, but none of these effects seemed to have a significant impact on pollination success. This study is an important step towards understanding the complexity of co-flowering community effects on the pollination success of individual plant species at multiple spatial scales. This study further reveals the potential importance of plant functional diversity in a community in helping predict competitive and facilitative interactions in co-flowering communities. Synthesis. Floral density and taxonomic and functional co-flowering diversity are important drivers of pollination success in flowering plants. The effects of the co-flowering diversity on the pollination success of plant species can largely depend on the spatial scale being studied. Only evaluating the outcomes of pollinator-mediated plant–plant interactions at multiple stages of the pollination process can lead to a complete understanding of their ecological consequences in nature.

No two species can indefinitely occupy the same ecological niche according to the competitive exclusion principle. When competing strains of the same pathogen invade a homogeneous population, the strain with the largest basic reproductive ratio R0 will force the other strains to extinction. However, over 51 pathogens are documented to have multiple strains [3] coexisting, contrary to the results from homogeneous models. In reality, the world is heterogeneous with the population varying in susceptibility. As such, the study of epidemiology, and hence the problem of pathogen coexistence should entail heterogeneity. Heterogeneous models tend to capture dynamics such as resistance to infection, giving more accurate results of the epidemics. This study will focus on the behavior of multi-pathogen heterogeneous models and will try to answer the question: what are the conditions on the model parameters that lead to pathogen coexistence? The goal is to understand the mechanisms in heterogeneous populations that mediate pathogen coexistence. Using the moment closure method, Fleming et. al. [22] used a two pathogen heterogeneous model (1.9) to show that pathogen coexistence was possible between strains of the baculovirus under certain conditions. In the first part of our study, we consider the same model using the hidden keystone variable (HKV) method. We show that under some conditions, the moment closure method and the HKV method give the same results. We also show that pathogen coexistence is possible for a much wider range of parameters, and give a complete analysis of the model (1.9), and give an explanation for the observed coexistence. The host population (gypsy moth) considered in the model (1.9) has a year life span, and hence, demography was introduced to the model using a discrete time model (1.12). In the second part of our study, we will consider a multi-pathogen compartmental heterogeneous model (3.1) with continuous time demography. We show using a Lyapunov function that pathogen coexistence is possible between multiple strains of the same pathogen. We provide analytical and numerical evidence that multiple strains of the same pathogen can coexist in a heterogeneous population.

In a distributed wireless system, multiple network nodes behave cooperatively towards a common goal. Though such assumptions on cooperation are desirable (e.g., controlling the transmit power level, reducing interference for each other, revealing private information, adhering to network policies) for analyzing and modeling, certain nodes belonging to a real-world system have often shown to deviate. These nodes, known as misbehaving nodes, bring more challenges to the design of the wireless network because the unreliable channel makes the actions of the nodes hidden from each other. In this dissertation, we analyze two types of misbehavior, namely, selfish noncooperation and malicious attacking. We apply game theoretic techniques to model the interactions among the nodes in the network. First, we consider a homogeneous unreliable channel and analyze the necessary and sufficient conditions to enforce cooperative packet forwarding among a node pair. We formulate an anti-collusion game and derive the conditions that achieve full cooperation when the non-cooperative nodes collude. In addition, we consider multi-hop communication with a heterogeneous channel model. We refine our game model as a hidden action game with imperfect private monitoring. A state machine based strategy is proposed to reach Nash Equilibrium. The strategy attains cooperative packet forwarding with heterogeneous channel and requires only partial and imperfect information. Furthermore, it also enforces cooperation in multi-hop packet forwarding. To tackle the malicious attacks, we use Bayesian game analysis to show the existence of equilibrium in the detection game and argue that it might not be profitable to isolate the malicious nodes upon detection. We propose the concept of "coexistence with malicious nodes" by proving the co-existence equilibrium and derive the conditions that achieve the equilibrium. This research is further accomplished by extensive simulation studies. Simulation results illustrate the properties of the games and the derived equilibria. The results validate our design philosophy and clearly indicate that the proposed game theoretic solutions can be effectively used to enforce cooperation and mitigate attacks.

Colombia's protracted civil war between Marxist insurgencies and the state has brought grave consequences for the civilian population and the prospects for constructing a viable political community in the country. With up to 5 million internally displaced people, rampant impunity for perpetrators of crimes against humanity and human rights and International Humanitarian Law violations, dozens of politicians and countless members of the armed forces linked to paramilitary organizations, along with increasing social injustices and inequalities, Colombia presents a troubling social-political panorama that has led to what is often referred to as a profound social and institutional 'moral crisis'. Much discussion has centred on the question of achieving some degree of minimal moral and political consensus and 'collective conscience' to humanize and slowly transform the conflict at local, regional and national levels. However, the philosophical and political parameters of this discussion have been and continue to be set firmly within variants of the liberal tradition which, it is argued, does not provide the necessary resources for adequately conceptualizing the problem and conceiving the task of addressing conflict, constructing moral consensus, and seeking social and political coexistence. The thesis argues that the philosophy of Alasdair MacIntyre can provide such resources. MacIntyre provides a convincing account of the philosophical problems that underlie ongoing intractable disagreement and the conflicts it breeds, offering a philosophy that can inform and underpin efforts at social transformation, resistance, and coexistence as well as aiding the necessary task of social scientific research and analysis of the conflict. The thesis analyses the moral dimensions of the conflict in light of MacIntyre's philosophy but also critically explores the adequacy of his politics of local community for the Colombian context. MacIntyre argues that a rational political community can only be constructed through the praxis of local communities engaging in shared moral-political deliberation. Through an empirical case study of a Constituent Assembly process in a rural community that has suffered the impacts of armed conflict for decades, the thesis explores an attempt at constructing peaceful social and political coexistence in light of MacIntyre's moral-sociological framework. / Economic and Social Research Council

Like many former colonised countries, Haiti has been plagued by insecurity and conflicts caused by internal and external influences as well as natural disasters. In 1804, after a protracted conflict between slaves and French colonialists, Haiti became the first black country to gain its independence through a revolution. Today, Haiti is the poorest country in the Western hemisphere, ranking 153rd on the Human Development Index and a significant number of humanitarian organisations are present on the island aspiring at improving the standard of living of the population. The following study examines how the relationships of power emerging through the relationship between humanitarian and local leaders affect their perceptions of each other and identified the emotions emerging from these perceptions. The perceptions identified are the coloniality of power, corruption and distrust, the occurrence of conspiracy theories and the obstacles encountered in the implementation of a relief-development continuum model envisioned by general humanitarian policies. These perceptions create tensions between the humanitarian and local leaders, contributing to fuelling negative emotions such as regret, sadness, sense of failure, disappointment and anger. Negative emotions in this study affect the collaboration between humanitarians and local leaders, diminishing the positive influences and impact of humanitarian action on the well-being of the Haitian population. One of the components to increase these positive influences of humanitarian action is to lessen the asymmetricality of power between humanitarian and local leaders through the adoption of a Cultural Competence model by humanitarians.

No description available.

Bridging knowledge systems is a potential means of equitably and collaboratively working towards shared goals in aquatic ecosystems, such as the management of invasive species. Invasive species pose a significant threat to aquatic ecosystems, and one example of an invasive species with an established control program are sea lamprey (Petromyzon marinus) within the Laurentian Great Lakes. Sea lamprey management faces many challenges including climate change and the apparent declining social acceptance of control programs, especially amongst Indigenous communities in the region. Such challenges illustrate the need for sea lamprey management to better engage Indigenous Nations and knowledge systems. Etuaptmumk (Two-Eyed Seeing) is a Mi’kmaw concept that can facilitate knowledge bridging as it enables Indigenous and Western knowledge systems to work together in parallel on a shared issue. This thesis research uses social science and Indigenous methodologies to understand the Denny’s Dam rehabilitation (sea lamprey barrier) as a case study for relationship-building and knowledge coexistence between Indigenous and non-Indigenous parties in sea lamprey control. Virtual semi-structured interviews (n = 14) were conducted with key decision-makers and others involved in the Denny’s Dam rehabilitation. Results illustrated why and how a knowledge coexistence approach (e.g. Two-Eyed Seeing) could bridge knowledge systems to inform a shared decision-making process. Moreover, findings outline four main factors needed for relationship-building. This study provides practical guidance for practitioners and addresses a gap in the literature concerning Indigenous engagement in sea lamprey management and knowledge coexistence/Two-Eyed Seeing in aquatic invasive species management.

Phase field modeling and simulation is employed to study the underlying mechanism of enhancing electromechanical properties in single crystals and polycrystals of perovskite-type ferroelectrics around the morphotropic phase boundary (MPB). The findings include: (I) Coherent phase decomposition near MPB in PZT is investigated. It reveals characteristic multidomain microstructures, where nanoscale lamellar domains of tetragonal and rhombohedral phases coexist with well-defined crystallographic orientation relationships and produce coherent diffraction effects. (II) A bridging domain mechanism for explaining the phase coexistence observed around MPBs is presented. It shows that minor domains of metastable phase spontaneously coexist with and bridge major domains of stable phase to reduce total system free energy, which explains the enhanced piezoelectric response around MPBs. (III) We demonstrate a grain size- and composition-dependent behavior of phase coexistence around the MPBs in polycrystals of ferroelectric solid solutions. It shows that grain boundaries impose internal mechanical and electric boundary conditions, which give rise to the grain size effect of phase coexistence, that is, the width of phase coexistence composition range increases with decreasing grain sizes. (IV) The domain size effect is explained by the domain wall broadening mechanism. It shows that, under electric field applied along the nonpolar axis, without domain wall motion, the domain wall broadens and serves as embryo of field-induced new phase, producing large reversible strain free from hysteresis. (V) The control mechanisms of domain configurations and sizes in crystallographically engineered ferroelectric single crystals are investigated. It reveals that highest domain wall densities are obtained with intermediate magnitude of electric field applied along non-polar axis of ferroelectric crystals. (VI) The domain-dependent internal electric field associated with the short-range ordering of charged point defects is demonstrated to stabilize engineered domain microstructure. The internal electric field strength is estimated, which is in agreement with the magnitude evaluated from available experimental data. (VII) The poling-induced piezoelectric anisotropy in untextured ferroelectric ceramics is investigated. It is found that the maximum piezoelectric response in the poled ceramics is obtained along a macroscopic nonpolar direction; and extrinsic contributions from preferred domain wall motions play a dominant role in piezoelectric anisotropy and enhancement in macroscopic nonpolar direction. (VIII) Stress effects on domain microstructure are investigated for the MPB-based ferroelectric polycrystals. It shows that stress alone cannot pole the sample, but can be utilized to reduce the strength of poling electric field. (IX) The effects of compressions on hysteresis loops and domain microstructures of MPB-based ferroelectric polycrystals are investigated. It shows that longitudinal piezoelectric coefficient can be enhanced by compressions, with the best value found when compression is about to initiate the depolarization process. / Ph. D.

In recent years, an increasing number of devices have been developed for operation in the bands allocated by the Federal Communications Commission (FCC) for license-free operation. Given the rules governing devices in these bands, it is possible for interference created by these devices to significantly reduce the overall capacity of these bands. Two such protocols are Bluetooth and IEEE 802.11b. Several methods have been presented in the literature for managing interference between these two devices. However, these approaches are generally not practical, since they either require the purchase of specialized hardware or do not comply with the current versions of existing protocols. In this dissertation, an approach is presented that is not only backwards-compatible, but requires the algorithm to be implemented in only a small subset of the devices operating in the local environment for the coexistence algorithm to function properly. An analytical solution for this coexistence approach when applied to generic networks is presented. A method is also presented for the backwards-compatible integration of some medium access control (MAC) protocols into Bluetooth devices. A case study of the Bluetooth/IEEE 802.11b coexistence problem is presented in this dissertation, as well as a proposed coexistence mechanism, collision-based multiple access (CBMA). A form of adaptive frequency hopping (AFH) is presented in this dissertation, as well as a combined CBMA/AFH strategy. The CBMA algorithm is shown be able to significantly reduce the impact of a Bluetooth link on an IEEE 802.11b link. The AFH algorithm is shown to have comparable performance to the CBMA algorithm. A combined CBMA/AFH algorithm presented, is shown to not only have an impact on the IEEE 802.11b link that is not greater than the CBMA-only implementation, but the Bluetooth link throughput is shown to be significantly greater than either the CBMA or AFH implementation alone. / Ph. D.

The radio spectrum that can be used for wireless communications is a finite but extremely valuable resource. During the past two decades, with the proliferation of new wireless applications, the use of the radio spectrum has intensified to the point that improved spectrum sharing policies and new mechanisms are needed to enhance its utilization efficiency. This dissertation studies spectrum sharing and coexistence on both licensed and unlicensed bands for wireless networks. For licensed bands, we study two coexistence paradigms: transparent coexistence (a.k.a., underlay) and policy-based network cooperation (a.k.a., overlay). These two paradigms can offer significant improvement in spectrum utilization and throughput performance than the interweave paradigm. For unlicensed band, we study coexistence of Wi-Fi and LTE, the two most poplar wireless networks. / Ph. D.