We can affirm to apprehend a system in its totality only when we know how it behaves under its natural operating conditions. However, in the face of the complexity of the world, science can only evolve by simplifications, which paradoxically hide a good deal of the very mechanisms we are interested in. On the other hand, scientific enterprise is very tightly related to the advances in technology and the latter inevitably influences the manner in which the scientific experiments are conducted. Due to this factor, experimental conditions which would have been impossible to bring into laboratory not more than 20 years ago, are today within our reach. This thesis investigates neuronal integrative processes by using a variety of theoretical and experimental techniques wherein the approximation of ecologically relevant conditions within the laboratory is the common denominator. The working hypothesis of this thesis is that neurons and neuronal systems, in the sensory and higher cortices, are specifically adapted, as a result of evolutionary processes, to the sensory signals most likely to be received under ecologically relevant conditions. In order to conduct the present study along this line, we first recorded movies with the help of two microcameras carried by cats exploring a natural environment. This resulted in a database of binocular natural movies that was used in our theoretical and experimental studies. In a theoretical study, we aimed to understand the principles of binocular disparity encoding in terms of spatio-temporal statistical properties of natural movies in conjunction with simple mathematical expressions governing the activity levels of simulated neurons. In an unsupervised learning scheme, we used the binocular movies as input to a neuronal network and obtained receptive fields that represent these movies optimally with respect to the temporal stability criterion. Many distinctive aspects of the binocular coding in complex cells, such as the phase and position encoding of disparity and the existence of unbalanced ocular contributions, were seen to emerge as the result of this optimization process. Therefore we conclude that the encoding of binocular disparity by complex cells can be understood in terms of an optimization process that regulates activities of neurons receiving ecologically relevant information. Next we aimed to physiologically characterize the responses of the visual cortex to ecologically relevant stimuli in its full complexity and compare these to the responses evoked by artificial, conventional laboratory stimuli. To achieve this, a state-of-the-art recording method, voltage-sensitive dye imaging was used. This method captures the spatio-temporal activity patterns within the millisecond range across large cortical portions spanning over many pinwheels and orientation columns. It is therefore very well suited to provide a faithful picture of the cortical state in its full complexity. Drifting bar stimuli evoked two major sets of components, one coding for the position and the other for the orientation of the grating. Responses to natural stimuli involved more complex dynamics, which were locked to the motion present in the natural movies. In response to drifting gratings, the cortical state was initially dominated by a strong excitatory wave. This initial spatially widespread hyper-excitatory state had a detrimental effect on feature selectivity. In contrast, natural movies only rarely induced such high activity levels and the onset of inhibition cut short a further increase in activation level. An increase of 30% of the movie contrast was estimated to be necessary in order to produce activity levels comparable to gratings. These results show that the operating regime within which the natural movies are processed differs remarkably. Moreover, it remains to be established to what extent the cortical state under artificial conditions represents a valid state to make inferences concerning operationally more relevant input. The primary visual cortex contains a dense web of neuronal connections linking distant neurons. However the flow of information within this local network is to a large extent unknown under natural stimulation conditions. To functionally characterize these long-range intra-areal interactions, we presented natural movies also locally through either one or two apertures and analyzed the effects of the distant visual stimulation on the local activity levels. The distant patch had a net facilitatory effect on the local activity levels. Furthermore, the degree of the facilitation was dependent on the congruency between the two simultaneously presented movie patches. Taken together, our results indicate that the ecologically relevant stimuli are processed within a distinct operating regime characterized by moderate levels of excitation and/or high levels of inhibition, where facilitatory cooperative interactions form the basis of integrative processes. To gather better insights into the motion locking phenomenon and test the generalizability of the local cooperative processes toward larger scale interactions, we resorted to the unequalized temporal resolution of EEG and conducted a multimodal study. Inspired from the temporal properties of our natural movies, we designed a dynamic multimodal stimulus that was either congruent or incongruent across visual and auditory modalities. In the visual areas, the dynamic stimulation unfolded neuronal oscillations with frequencies well above the frequency spectrum content of the stimuli and the strength of these oscillations was coupled to the stimuli's motion profile. Furthermore, the coupling was found to be stronger in the case where the auditory and visual streams were congruent. These results show that the motion locking, which was so far observed in cats, is a phenomenon that also exists in humans. Moreover, the presence of long-range multimodal interactions indicates that, in addition to local intra-areal mechanisms ensuring the integration of local information, the central nervous system embodies an architecture that enables also the integration of information on much larger scales spread across different modalities. Any characterization of integrative phenomena at the neuronal level needs to be supplemented by its effects at the behavioral level. We therefore tested whether we could find any evidence of integration of different sources of information at the behavioral level using natural stimuli. To this end, we presented to human subjects images of natural scenes and evaluated the effect of simultaneously played localized natural sounds on their eye movements. The behavior during multimodal conditions was well approximated by a linear combination of the behavior under unimodal conditions. This is a strong indication that both streams of information are integrated in a joint multimodal saliency map before the final motor command is produced. The results presented here validate the possibility and the utility of using natural stimuli in experimental settings. It is clear that the ecological relevance of the experimental conditions are crucial in order to elucidate complex neuronal mechanisms resulting from evolutionary processes. In the future, having better insights on the nervous system can only be possible when the complexity of our experiments will match to the complexity of the mechanisms we are interested in.

This dissertation addresses five fundamental resource allocation problems on networks, all of which have applications to support Homeland Security or industry challenges. In the first application, we model and solve the strategic problem of minimizing the expected loss inflicted by a hostile terrorist organization. An appropriate allocation of certain capability-related, intent-related, vulnerability-related, and consequence-related resources is used to reduce the probabilities of success in the respective attack-related actions, and to ameliorate losses in case of a successful attack. Given the disparate nature of prioritizing capital and material investments by federal, state, local, and private agencies to combat terrorism, our model and accompanying solution procedure represent an innovative, comprehensive, and quantitative approach to coordinate resource allocations from various agencies across the breadth of domains that deal with preventing attacks and mitigating their consequences. Adopting a nested event tree optimization framework, we present a novel formulation for the problem as a specially structured nonconvex factorable program, and develop two branch-and-bound schemes based respectively on utilizing a convex nonlinear relaxation and a linear outer-approximation, both of which are proven to converge to a global optimal solution. We also investigate a fundamental special-case variant for each of these schemes, and design an alternative direct mixed-integer programming model representation for this scenario. Several range reduction, partitioning, and branching strategies are proposed, and extensive computational results are presented to study the efficacy of different compositions of these algorithmic ingredients, including comparisons with the commercial software BARON. The developed set of algorithmic implementation strategies and enhancements are shown to outperform BARON over a set of simulated test instances, where the best proposed methodology produces an average optimality gap of 0.35% (compared to 4.29% for BARON) and reduces the required computational effort by a factor of 33. A sensitivity analysis is also conducted to explore the effect of certain key model parameters, whereupon we demonstrate that the prescribed algorithm can attain significantly tighter optimality gaps with only a near-linear corresponding increase in computational effort. In addition to enabling effective comprehensive resource allocations, this research permits coordinating agencies to conduct quantitative what-if studies on the impact of alternative resourcing priorities. The second application is motivated by the author's experience with the U.S. Army during a tour in Iraq, during which combined operations involving U.S. Army, Iraqi Army, and Iraqi Police forces sought to interdict the transport of selected materials used for the manufacture of specialized types of Improvised Explosive Devices, as well as to interdict the distribution of assembled devices to operatives in the field. In this application, we model and solve the problem of minimizing the maximum flow through a network from a given source node to a terminus node, integrating different forms of superadditive synergy with respect to the effect of resources applied to the arcs in the network. Herein, the superadditive synergy reflects the additional effectiveness of forces conducting combined operations, vis-à-vis unilateral efforts. We examine linear, concave, and general nonconcave superadditive synergistic relationships between resources, and accordingly develop and test effective solution procedures for the underlying nonlinear programs. For the linear case, we formulate an alternative model representation via Fourier-Motzkin elimination that reduces average computational effort by over 40% on a set of randomly generated test instances. This test is followed by extensive analyses of instance parameters to determine their effect on the levels of synergy attained using different specified metrics. For the case of concave synergy relationships, which yields a convex program, we design an inner-linearization procedure that attains solutions on average within 3% of optimality with a reduction in computational effort by a factor of 18 in comparison with the commercial codes SBB and BARON for small- and medium-sized problems; and outperforms these softwares on large-sized problems, where both solvers failed to attain an optimal solution (and often failed to detect a feasible solution) within 1800 CPU seconds. Examining a general nonlinear synergy relationship, we develop solution methods based on outer-linearizations, inner-linearizations, and mixed-integer approximations, and compare these against the commercial software BARON. Considering increased granularities for the outer-linearization and mixed-integer approximations, as well as different implementation variants for both these approaches, we conduct extensive computational experiments to reveal that, whereas both these techniques perform comparably with respect to BARON on small-sized problems, they significantly improve upon the performance for medium- and large-sized problems. Our superlative procedure reduces the computational effort by a factor of 461 for the subset of test problems for which the commercial global optimization software BARON could identify a feasible solution, while also achieving solutions of objective value 0.20% better than BARON. The third application is likewise motivated by the author's military experience in Iraq, both from several instances involving coalition forces attempting to interdict the transport of a kidnapping victim by a sectarian militia as well as, from the opposite perspective, instances involving coalition forces transporting detainees between interment facilities. For this application, we examine the network interdiction problem of minimizing the maximum probability of evasion by an entity traversing a network from a given source to a designated terminus, while incorporating novel forms of superadditive synergy between resources applied to arcs in the network. Our formulations examine either linear or concave (nonlinear) synergy relationships. Conformant with military strategies that frequently involve a combination of overt and covert operations to achieve an operational objective, we also propose an alternative model for sequential overt and covert deployment of subsets of interdiction resources, and conduct theoretical as well as empirical comparative analyses between models for purely overt (with or without synergy) and composite overt-covert strategies to provide insights into absolute and relative threshold criteria for recommended resource utilization. In contrast to existing static models, in a fourth application, we present a novel dynamic network interdiction model that improves realism by accounting for interactions between an interdictor deploying resources on arcs in a digraph and an evader traversing the network from a designated source to a known terminus, wherein the agents may modify strategies in selected subsequent periods according to respective decision and implementation cycles. We further enhance the realism of our model by considering a multi-component objective function, wherein the interdictor seeks to minimize the maximum value of a regret function that consists of the evader's net flow from the source to the terminus; the interdictor's procurement, deployment, and redeployment costs; and penalties incurred by the evader for misperceptions as to the interdicted state of the network. For the resulting minimax model, we use duality to develop a reformulation that facilitates a direct solution procedure using the commercial software BARON, and examine certain related stability and convergence issues. We demonstrate cases for convergence to a stable equilibrium of strategies for problem structures having a unique solution to minimize the maximum evader flow, as well as convergence to a region of bounded oscillation for structures yielding alternative interdictor strategies that minimize the maximum evader flow. We also provide insights into the computational performance of BARON for these two problem structures, yielding useful guidelines for other research involving similar non-convex optimization problems. For the fifth application, we examine the problem of apportioning railcars to car manufacturers and railroads participating in a pooling agreement for shipping automobiles, given a dynamically determined total fleet size. This study is motivated by the existence of such a consortium of automobile manufacturers and railroads, for which the collaborative fleet sizing and efforts to equitably allocate railcars amongst the participants are currently orchestrated by the \textit{TTX Company} in Chicago, Illinois. In our study, we first demonstrate potential inequities in the industry standard resulting either from failing to address disconnected transportation network components separately, or from utilizing the current manufacturer allocation technique that is based on average nodal empty transit time estimates. We next propose and illustrate four alternative schemes to apportion railcars to manufacturers, respectively based on total transit time that accounts for queuing; two marginal cost-induced methods; and a Shapley value approach. We also provide a game-theoretic insight into the existing procedure for apportioning railcars to railroads, and develop an alternative railroad allocation scheme based on capital plus operating costs. Extensive computational results are presented for the ten combinations of current and proposed allocation techniques for automobile manufacturers and railroads, using realistic instances derived from representative data of the current business environment. We conclude with recommendations for adopting an appropriate apportionment methodology for implementation by the industry. / Ph. D.

Amharic literature has always occupied an important place in the history of the literary traditions of Ethiopia. Although this literature is believed to be strongly related to the politics of the country, there has been no study that proves this claim across the different political periods in the country. It would be ambitious to deal with all the literary genres in this respect. Therefore, delimiting the investigation of the problem is considered to be useful to filling the knowledge gap. Accordingly, this comparative research which investigates a representation of Ethiopian politics in selected Amharic novels across three political periods: 1930 – 2010 was designed. The objective of the research is to investigate the representation of Ethiopian politics in selected Amharic novels. The basic research question focuses on how these representations can be explained. An eclectic theoretical approach (the New Historicism, Bourdieu’s System Theory and the Critical Discourse Analysis) is employed to understand the representations. The main method of data collection focuses on a close reading of non-literary and literary texts. A purposive sampling technique is used to select the sample novels as the technique allows to select those that yield the most relevant data using some criteria. Based on the criteria set, sixteen novels are selected. The manners in which the political events represented in the novels are examined using different parameters. The parameters also look into the methods used in representing the political events and the time in which the events were represented, i.e. whether they are represented contemporarily, post-contemporarily or before the actual happening of the event. Having read the novels critically, the political events that took place in the three respective states are identified, analyzed and interpreted. The analysis mainly shows that different novels represented the political events in different manners: lightly or deeply, overtly or covertly, positively or negatively, contemporaneously or post-contemporaneously. Regarding the ‘how’ of the representations, it is observed that the critical novels, for instance, Alïwälädïm and Adäfrïs are covert and use symbols, direct and indirect allusions and other figures of speeches, and other techniques including turn taking, and size of dialogues to achieve their goals. Some political events are found to be either under-represented or totally un-represented in the novels. In some cases, same political events are represented differently in different novels at different times. Some novels that criticized the political events of the governments contemporaneously have been removed from market, republished in the political period that followed and exploited by the emerging government for its political end. There are some patterns observed in the analyses and interpretations of the politics in the novels. One of the patterns is that sharp criticisms on the events of an earlier political period are usually reflected in novels published in a new period. The critique novels of the Haileselassie government, for instance, Maïbäl Yabïyot Wazema, were published during the Darg period, and those that were critical of the Darg government, for instance, Anguz, were published in the EPRDF period. Another pattern observed is that there is no novel that praises a past regime, even despite being critical of a contemporary government. No novel written during the Darg period admired the Haileselassie period; and no novel written during the EPRDF period appreciated the Darg period. There are cases in which novelists who were critical of the contemporary Haileselassie and Darg periods, for instance, Abe and Bealu, respectively, ended up in detention or just disappeared and their novels, Alïwälädïm and Oromay, respecitely were banned from being circulated. Unlike the two previous political periods, the critique novels of the EPRDF period, for instance Dertogada, Ramatohara, and Yäburqa Zïmïta, have been published, or even republished, several times. Novels written during the Haileselassie period, such as Alïwälädïm, which were critical of the respective contemporary period, made their criticism covertly, using probes and imaginary settings and characters, while the critique novels of the EPRDF period, criticize overtly, and boldly. Generally, it could be concluded that the novels had the power to reflect history, and show human and class relationships implicitly, through the interactions of characters, story developments, and plot constructions, and the impact that politics has on the literature, and the influence of literature on politics. / Classics and World Languages / D. Phil. (Theory of Literature)

Anxiety can be advantageous in terms of survival and well-being, yet atypically high levels may be maladaptive and result in the clinical diagnosis of an anxiety disorder. Several risk factors have been implicated in the manifestation of clinical anxiety, including cognitive biases. In recent years, a plethora of research has emerged demonstrating that anxious adults exhibit biases of attention for threatening stimuli, especially that which is biologically relevant (e.g., facial expressions). Specific components of attentional bias have also been identified, namely facilitated engagement, impaired disengagement, and avoidance. However, the majority of studies have focused on the spatial domain of attention. Furthermore, the area is under-researched in children, despite research demonstrating that symptoms relating to clinical and non-clinical anxiety follow a stable course from childhood through to adolescence and adulthood. Consequently, the aim of this thesis was to investigate how anxiety affects children’s visual attention for emotive, particularly angry, faces. In order to provide a more comprehensive understanding, the current research involved examining the role of temporal and spatial attention utilising rapid serial visual presentation with the attentional blink, and the visual probe paradigm, respectively. The main hypothesis was that high state and/or trait anxiety would be associated with an attentional bias for angry, relative to positive or neutral faces in both the temporal and spatial domains. In relation to the temporal domain, key findings demonstrated that high levels of trait anxiety were associated with facilitated engagement towards both angry and neutral faces. It was further found that all children rapidly disengaged attention away from angry faces. Findings related to the processing of angry faces accorded with the main hypothesis stated in this thesis, as well as research and theory in the area. The finding that anxious children preferentially processed neutral faces in an attentional blink investigation was unexpected. This was argued to potentially reflect this stimulus type being interpreted as threatening. Key findings regarding the spatial domain were that high trait anxious children displayed an early covert bias of attention away from happy faces and a later, overt bias of attention away from angry faces. The finding that high trait anxiety was linked to an attentional bias away from happy faces in a visual probe task was also unexpected. This was argued to potentially reflect smiling faces being interpreted as signifying social dominance, thus resulting in the viewer experiencing feelings of subordination and becoming avoidant and/or submissive. To conclude, this thesis has enhanced current knowledge of attentional bias in both the temporal and spatial domains for emotive stimuli in anxious children. It has demonstrated that higher levels of trait anxiety moderate children’s allocation of attentional resources to different stimulus types, whether these are threatening, positive, or neutral. This has important implications for evaluating past research in adults and children, and for further developing theoretical models of attentional bias and anxiety. It also offers important clinical implications, since attending towards or away from specific stimuli may affect the development and maintenance of anxiety disorders. Recently, a treatment that aims to modify attentional bias in anxious individuals has begun to be developed. In light of the present findings, it may be necessary to review this treatment so that anxious children are re-trained in the specific biases of attention demonstrated here.

Amharic literature has always occupied an important place in the history of the literary traditions of Ethiopia. Although this literature is believed to be strongly related to the politics of the country, there has been no study that proves this claim across the different political periods in the country. It would be ambitious to deal with all the literary genres in this respect. Therefore, delimiting the investigation of the problem is considered to be useful to filling the knowledge gap. Accordingly, this comparative research which investigates a representation of Ethiopian politics in selected Amharic novels across three political periods: 1930 – 2010 was designed. The objective of the research is to investigate the representation of Ethiopian politics in selected Amharic novels. The basic research question focuses on how these representations can be explained. An eclectic theoretical approach (the New Historicism, Bourdieu’s System Theory and the Critical Discourse Analysis) is employed to understand the representations. The main method of data collection focuses on a close reading of non-literary and literary texts. A purposive sampling technique is used to select the sample novels as the technique allows to select those that yield the most relevant data using some criteria. Based on the criteria set, sixteen novels are selected. The manners in which the political events represented in the novels are examined using different parameters. The parameters also look into the methods used in representing the political events and the time in which the events were represented, i.e. whether they are represented contemporarily, post-contemporarily or before the actual happening of the event. Having read the novels critically, the political events that took place in the three respective states are identified, analyzed and interpreted. The analysis mainly shows that different novels represented the political events in different manners: lightly or deeply, overtly or covertly, positively or negatively, contemporaneously or post-contemporaneously. Regarding the ‘how’ of the representations, it is observed that the critical novels, for instance, Alïwälädïm and Adäfrïs are covert and use symbols, direct and indirect allusions and other figures of speeches, and other techniques including turn taking, and size of dialogues to achieve their goals. Some political events are found to be either under-represented or totally un-represented in the novels. In some cases, same political events are represented differently in different novels at different times. Some novels that criticized the political events of the governments contemporaneously have been removed from market, republished in the political period that followed and exploited by the emerging government for its political end. There are some patterns observed in the analyses and interpretations of the politics in the novels. One of the patterns is that sharp criticisms on the events of an earlier political period are usually reflected in novels published in a new period. The critique novels of the Haileselassie government, for instance, Maïbäl Yabïyot Wazema, were published during the Darg period, and those that were critical of the Darg government, for instance, Anguz, were published in the EPRDF period. Another pattern observed is that there is no novel that praises a past regime, even despite being critical of a contemporary government. No novel written during the Darg period admired the Haileselassie period; and no novel written during the EPRDF period appreciated the Darg period. There are cases in which novelists who were critical of the contemporary Haileselassie and Darg periods, for instance, Abe and Bealu, respectively, ended up in detention or just disappeared and their novels, Alïwälädïm and Oromay, respecitely were banned from being circulated. Unlike the two previous political periods, the critique novels of the EPRDF period, for instance Dertogada, Ramatohara, and Yäburqa Zïmïta, have been published, or even republished, several times. Novels written during the Haileselassie period, such as Alïwälädïm, which were critical of the respective contemporary period, made their criticism covertly, using probes and imaginary settings and characters, while the critique novels of the EPRDF period, criticize overtly, and boldly. Generally, it could be concluded that the novels had the power to reflect history, and show human and class relationships implicitly, through the interactions of characters, story developments, and plot constructions, and the impact that politics has on the literature, and the influence of literature on politics. / Classics and World Languages / D. Phil. (Theory of Literature)

The multiliteracies pedagogy of the New London Group is a response to the emergence of new literacies and changing forms of meaning-making in contemporary contexts of increased cultural and linguistic diversity. This critical ethnographic research investigates the interactions between pedagogy, power, discourses, and differential access to multiliteracies, among a group of culturally and linguistically diverse learners in a mainstream Australian classroom. The study documents the way in which a teacher enacted the multiliteracies pedagogy through a series of mediabased lessons with her year six (aged 11-12 years) class. The reporting of this research is timely because the multiliteracies pedagogy has become a key feature of Australian educational policy initiatives and syllabus requirements. The methodology of this study was based on Carspecken's critical ethnography. This method includes five stages: Stage One involved eighteen days of observational data collection over the course of ten weeks in the classroom. The multiliteracies lessons aimed to enable learners to collaboratively design a claymation movie. Stage Two was the initial analysis of data, including verbatim transcribing, coding, and applying analytic tools to the data. Stage Three involved semi-structured, forty-five minute interviews with the principal, teacher, and four culturally and linguistically diverse students. In Stages Four and Five, the results of micro-level data analysis were compared with macro-level phenomena using structuration theory and extant literature about access to multiliteracies. The key finding was that students' access to multiliteracies differed among the culturally and linguistically diverse group. Existing degrees of access were reproduced, based on the learners' relation to the dominant culture. In the context of the media-based lessons in which students designed claymation movies, students from Anglo-Australian, middle-class backgrounds had greater access to transformed designing than those who were culturally marginalised. These experiences were mediated by pedagogy, power, and discourses in the classroom, which were in turn influenced by the agency of individuals. The individuals were both enabled and constrained by structures of power within the school and the wider educational and social systems. Recommendations arising from the study were provided for teachers, principals, policy makers and researchers who seek to monitor and facilitate the success of the multiliteracies pedagogy in culturally and linguistically diverse educational contexts.