INTRODUCTION: Major depressive disorder (MDD) is characterized by ongoing feelings of guilt, sadness, and memory and cognition impairment. It is a multidimensional illness that affects many functionally integrated pathways of the brain. Understanding the underlying brain dysfunction that gives rise to this complex illness has been challenging, and by extension the search for appropriate treatments. MDD patients who are considered treatment resistant make up the primary population that receives electroconvulsive therapy (ECT). Remarkably, ECT shows a 75% remission rate in this patient population and is considered the “gold standard” treatment for major depression. Although the exact mechanism of its function is unknown, it is well accepted that the induced grand-mal seizure confers its therapeutic effect. The seizure likely has broad effect that somehow corrects the underlying dysfunction in brain circuitry. Here, we specifically examined studies of functional connectivity and metabolite changes. METHODS: Through literature search, we examined six studies in functional connectivity and four studies in magnetic resonance spectroscopy (MRS). RESULTS: Functional Connectivity: Studies have found that after bilateral ECT treatments, patients with major depression showed reduction of functional connectivity (FC) from the left dorsolateral prefrontal cortex (DLPFC) to other cortical and limbic structures. Correlated activity between the superior frontal gyri, middle frontal gyri and angular gyri were significantly increased after ECT. Hyperdeactivation of the orbitofrontal cortex to negative emotional stimuli in patients was decreased, and it was associated with improvement in depressive symptoms. Regional activity in the subgenual anterior cingulate cortex (sgACC) and functional connectivity between the sgACC and left hippocampus in treatment naïve patients after ECT were increased and correlated to reduction of depressive symptoms. Reduced connectivity between the amygdale and sgACC and increased connectivity between the amygdale and DLPFC was found by sequential assessments over a course of ECT treatments. Lastly, ECT increased the functional connectivity between DLPFC and the default mode network. MRS: Studies found decreased levels of glutamate or glx (glutamate/glutamine/ GABA) in patients in the anterior cingulate cortex and dorsolateral prefrontal cortex (DLPFC) compared to healthy controls. Additionally, it was found that glx levels increased after ECT treatments and that this increase was only in those who responded to treatment. Lastly, GABA level increased after ECT treatment in the occipital cortex. Discussion: Results from functional connectivity and brain metabolite studies in patients with major depression point to induced neuroplasticity as part of ECT’s therapeutic mechanism. Remodeling connectivity and mediating metabolite changes both will require modifications at the synaptic level. The wide spread changes seen in several different brain regions that have been implicated in depression further suggests that ECT’s effects are both highly specific and broad. CONCLUSION: Electroconvulsive therapy has consistently demonstrated impressive efficacy among the most severely depressed patients and is known to produce widely distributed effects in the brain. However, this also makes assessing its therapeutic mechanism challenging. Magnetic resonance imaging studies assessing functional connectivity and brain metabolite levels have demonstrated that ECT likely produces neuroplastic changes to remodel aberrant connectivity and dysfunctional excitatory and inhibitory neurotransmission in cortical and limbic areas. Although these findings should be interpreted with caution, this field of research has provided an unprecedented opportunity to examine the living brain in great detail. Further studies with larger sample sizes and improved technical specifications will likely yield greater results.

abstract: The use of energy-harvesting in a wireless sensor network (WSN) is essential for situations where it is either difficult or not cost effective to access the network's nodes to replace the batteries. In this paper, the problems involved in controlling an active sensor network that is powered both by batteries and solar energy are investigated. The objective is to develop control strategies to maximize the quality of coverage (QoC), which is defined as the minimum number of targets that must be covered and reported over a 24 hour period. Assuming a time varying solar profile, the problem is to optimally control the sensing range of each sensor so as to maximize the QoC while maintaining connectivity throughout the network. Implicit in the solution is the dynamic allocation of solar energy during the day to sensing and to recharging the battery so that a minimum coverage is guaranteed even during the night, when only the batteries can supply energy to the sensors. This problem turns out to be a non-linear optimal control problem of high complexity. Based on novel and useful observations, a method is presented to solve it as a series of quasiconvex (unimodal) optimization problems which not only ensures a maximum QoC, but also maintains connectivity throughout the network. The runtime of the proposed solution is 60X less than a naive but optimal method which is based on dynamic programming, while the peak error of the solution is less than 8%. Unlike the dynamic programming method, the proposed method is scalable to large networks consisting of hundreds of sensors and targets. The solution method enables a designer to explore the optimal configuration of network design. This paper offers many insights in the design of energy-harvesting networks, which result in minimum network setup cost through determination of optimal configuration of number of sensors, sensing beam width, and the sampling time. / Dissertation/Thesis / M.S. Computer Science 2012

To understand how the brain functions, we must investigate the transient interactions that underpin communication between cortical regions. EEG possesses the optimal temporal resolution to capture functional connectivity, but it lacks the spatial resolution to identify the cortical locations responsible. To circumvent this problem electrophysiological connectivity should be investigated at the source level. There are many quantifiers of connectivity applied to EEG data, but some are not sensitive to the direct, or indirect, influence of one region over another, and others require the specification of a priori models so are unsuitable for exploratory analyses. Transfer Entropy (TE) can be used to infer the direction of linear and non-linear information exchange between signals over a range of time-delays within EEG data. This thesis explores the creation of a new method of mapping dynamic brain connectivity using a trial-based TE analysis of EEG source data, and the application of this technique to the investigation of semantic and number processing within the brain. The first paper (Chapter 2) documents the analyses of a semantic category and number magnitude judgement task using traditional ERP techniques. As predicted, the well-known semantic N400 component was found, and localised to left ATL and inferior frontal cortex. An N365 component related to number magnitude judgement was localised to right superior parietal regions including the IPS. These results offer support for the hub-and-spoke model of semantics, and the triple parietal model of number processing. The second paper (Chapter 3) documents an analysis of the same data with the new trial-based TE analysis. Word and number data were analysed at 0-200ms, 200-400ms, and 400-600ms following stimulus presentation. In the earliest window, information exchange was occurring predominately between occipital sources, but by the latest window it had become spread out across the brain. Task-dependent differences of regional information exchange revealed that temporal sources were sending more information to occipital sources following words at 0-200ms. Furthermore, the direction and timing of information movement within a front-temporal-parietal network was identified during 0-400ms of the number magnitude judgment. The final paper (Chapter 4), documents an attempt to track the influence of TMS through the brain using the TE analysis. TMS was applied to bilateral ATL and IPS because they are both important hubs in the brain networks that support semantic and number processing respectively. Left ATL TMS influenced sources located primarily in wide-spread left temporal lobe, and inferior frontal and inferior occipital cortices. The anatomical connectivity profile of the temporal lobe suggests that these are all plausible locations, and they exhibited excellent spatial similarities to the results of neuroimaging experiments that probed semantic knowledge. The analysis of right ATL TMS obtained a mirror image of the left. Left parietal stimulation resulted in a bilateral parietal, superior occipital, and superior prefrontal influence, which extended slightly further in the ipsilateral hemisphere to stimulation site. A result made possible by the short association and callosal fibres that connect these areas. Again, the results at the contralateral site were a virtual mirror image. The thesis concludes with a review of the experimental findings, and a discussion of methodological issues still to be resolved, ideas for extensions to the method, and the broader implications of the method on connectivity research.

The genus Sorbus is an example of a taxonomically complex group (TCG) with diversity derived from hybridisation, polyploidy and apomixis. The focus of this study was to elucidate the evolutionary relationships among nine Sorbus species including endemics of the Devon and north Somerset region of the south west UK, determine main routes of polyploid formation and investigate reproductive sustainability in order to make recommendations for Sorbus conservation. Molecular analysis showed that genetic structure patterns and genotypic diversity support the hypothesis that the study polyploids are a product of rare interspecific hybridisation, of single origins and are maintained through apomictic reproduction. PCoA, Neighbour Joining analysis and parental simulations reveal a reticulated relationship, with diversification the result of hybridisations between sexual diploid Sorbus torminalis and both tetraploid and triploid species. Hybridisation between S. torminalis and tetraploid Sorbus margaretae (subgenus Aria) have likely given rise to the study members of subgenus Tormaria through production of a triploid which has subsequently backcrossed to Sorbus torminalis to form further tetraploids. The discovery of a cryptic hybrid in subgenus Aria also suggests occasional hybridisation events among tetraploids are a possible route for further tetraploid formation These events illustrate key routes of polyploid formation, both illustrating the role of triploids in tetraploid formation via the triploid bridge and the key role in sexual diploids in diversification in Sorbus. Hand pollination experiments showed that self-incompatibility in the triploid species (Sorbus subcuneata) means reliance on congeneric pollen from sympatric tetraploid species for seed production. Reproductive sustainability in this species is severely compromised through spatial isolation from compatible congeners. Our findings are strong support for the development of conservation strategies that aim to safeguard current diversity through actions that increase reproductive sustainability and recruitment opportunities, and promote opportunities for on-going hybridisation for future diversification of Sorbus in this region.

Functional magnetic resonance imaging studies have long demonstrated a high degree of correlated activity between the left and right hemispheres of the brain. Interregional correlations between the time series of each brain voxel or region and its homotopic pair have recently been identified by methods such as homotopic resting-state functional connectivity (H-RSFC). However, little is known about whether interhemispheric regions in patients with Attention-deficit/hyperactivity disorder (ADHD) are functionally abnormal. The aim of this thesis is to examine the association between H-RSFC and medication status, age, sex, and volumetric asymmetry index (AI). In our approach, region-based activity was obtained using three different methods. To test for associations, two linear mixed-effects models were used. Across results, H-RSFC variation was found in subcortical regions and portions of cortical regions. In addition, changes in functional connectivity were found to be linked with structural asymmetry in two cortical regions. More importantly, shifting in homotopic functional activation was found as a result of medication intake in youths with ADHD. These findings demonstrate the utility of homotopic resting-state functional connectivity for measuring differences among pharmacotherapy intake, gender, neurodevelopment, and structural asymmetry.

Indiana University-Purdue University Indianapolis (IUPUI) / With the fast development of 5G networks and the advancement in networking technologies, more and more new technologies such as internet of vehicles (IoV) is catching our eyes. With technologies of artificial intelligence and automatic control, IoV is transformed into an intelligent transportation system (ITS). The object of this thesis is to analyze the connectivity probability issues in vehicle ad hoc networks (VANETs), which is a subset of ITS. This will be achieved by a platoon-based two dimensional model. In order to make the results more accurate and more close to real scenario, different situations will be analyzed separately, and different types of platoon will be included. In addition, other system parameters are also discussed and stimulated. The results show that many parameters like the increases of traffic density, ratio of platoon, and lane numbers will improve connectivity probability. No-leader based platoons are easier to connect to the base stations compared to leader based platoons.

In everyday settings, spatial attention helps listeners isolate and understand individual sound sources. However, the neural mechanisms of auditory spatial attention (ASpA) are only partially understood. This thesis uses within-subject analysis of functional magnetic resonance imaging (fMRI) data to address fundamental questions regarding cortical mechanisms supporting ASpA by applying novel multi-voxel pattern analysis (MVPA) and resting-state functional connectivity (rsFC) approaches. A series of fMRI studies of ASpA were conducted in which subjects performed a one-back task in which they attended to one of two spatially separated streams. Attention modulated blood oxygenation level-dependent (BOLD) activity in multiple areas in the prefrontal, temporal, and parietal cortex, including non-visuotopic intraparietal sulcus (IPS), but not the visuotopic maps in IPS. No spatial bias was detected in any cortical area using standard univariate analysis; however, MVPA revealed that activation patterns in a number of areas, including the auditory cortex, predicted the attended direction. Furthermore, we explored how cognitive task demands and the sensory modality of the inputs influenced activity with a visual one-back task and a visual multiple object tracking (MOT) task. Activity from the visual and auditory one-back tasks overlapped along the fundus of IPS and lateral prefrontal cortex (lPFC). However, there was minimal overlap of activity in the lPFC between the visual MOT task and the two one-back tasks. Finally, we endeavored to identify visual and auditory networks using rsFC. We identified a dorsal visual attention network reliably within individual subjects using visuotopic seeds. Using auditory seeds, we found a prefrontal area nested between segments of the dorsal visual attention network. These findings mark fundamental progress towards elucidating the cortical network controlling ASpA. Our results suggest that similar lPFC structures support both ASpA and its visual counterpart during a spatial one-back task, but that ASpA does not drive visuotopic IPS in the parietal cortex. Furthermore, rsFC reveals that visual and auditory seed regions are functionally connected with non-overlapping lPFC regions, possibly reflecting spatial and temporal cognitive processing biases, respectively. While we find no evidence for a spatiotopic map, the auditory cortex is sensitive to direction of attention in its patterns of activation.

Speed has long been equated with "progress". The Romans' paved roads begot much of this concept, allowing faster travel that improved communication, commerce, and enabled control over vast territories. Additionally paved surfaces whisked insect-breeding water away from homes, improving the health of those in town. Today, part-and-parcel of the definition of the developed world are tremendous amounts of solid surfaces, mostly asphalt and concrete, to move mechanized devices and water quickly. Even the shoes we wear could be seen as complementary technological devices, cushioning our feet to allow us to barrel forward more quickly along firm, manmade foundations. But the push towards this progress has had destructive consequences on our environment, including, but not limited to, our stream valleys. Often abutting intense, impervious development, the stream valley watersheds have morphed from spongy spines dense with aquatic life to de-facto storm sewers, with thick foliage merely masking severe erosion and paltry ecosystems. Quite simply, the speed at which the water is pushed down the ever-narrowed corridors as paved development encroaches, coupled with pollution from this fast runoff, renders the former fish streams dead. The recent advent of nature trails (following a mix of old hunting paths and former gristmill horse-cart ways), along unbuildable flood plains has exposed this problem in the Accotink stream valley in Northern Virginia. This thesis addresses the topic of water runoff of the Accotink stream valley and trail network. After analyzing and studying the area as a whole, the thesis focused on two scales: the larger scale of Fairfax Circle in Fairfax City in suburban Northern Virginia and a piece of this area -- a small section that acts as a threshold from urban village to natural park/trail/creek bed. This smaller section is also along the most eroded section of the Accotink Creek. At the "master plan" scale, the thesis transforms Fairfax Circle to a "village" using environmental remediation design principals to repair and regenerate this environmentally-degraded area. At the architectural scale, the thesis examines the site through the lens of the regional trail network along the stream valleys and the potential urban village at Fairfax Circle to design a trail-stop fitness center that straddles the break between conceptual urban space and repaired, stormwater-soaking stream valley. / Master of Architecture

Magister Scientiae (Integrated Water Resource Management) / The heterogeneity in groundwater systems suggest that not all aquifers are connected in groundwater systems. This study is about the interaction between aquifers within groundwater system. Langebaan Road and Elandsfontein aquifers in the West Coast groundwater aquifer system were chosen as case studies. These units were chosen because the previous studies on groundwater excluded the aspect of connectivity between aquifers from methods perspective which is the focus on the current study. The second reason for the study area was the present of human activities and ecosystems which are proved to be groundwater dependents. Aquifer-aquifer interaction refers to hydraulic connection between two aquifers. The interaction is influenced by hydraulic pressure and lithology of geological strata, their integrity and spatial continuity. While factors for such connectivity are well known, appropriate techniques to establish the extent of connectivity remain poorly understood and hence the need to employ various techniques so that the extent of connectivity between the two aquifers is established. Understanding the connectivity between aquifers is important because such connectivity explains the pathways for the availability of groundwater in each aquifer unit and the associated groundwater quality in each unit that supports human activities and sustain ecological systems.

Submitted in accordance with the requirements for the degree of Master of Arts in Communication Science at the University of Zululand, South Africa, 2012. / It is everyone’s dream to have network connectivity all the time. This dream can only be realised provided there are feasible solutions that are put in place for the next generation of wireless works. Wireless Mesh Networking (WMN) is therefore seen as a solution to the next generation of wireless networks because of the fact that WMNs configures itself and it is also self healing. A new standard for WMNs called the IEEE 802.11s is still under development. The protocol that is used by the IEEE 802.11s for routing is called Hybrid Wireless Mesh Protocol (HWMP). The main purpose of HWMP is to perform routing at layer-2 of the OSI model also referred to as the data link layer (DLL). Layer-2 routing is also referred to as the mesh path selection and forwarding. Devices that are compliant to the IEEE 802.11s standard will be able to use this path selection protocol. Devices that are manufactured by different vendors will therefore be interoperable. Even though significant efforts have gone into improving the performance of HWMP, the protocol still faces a lot of limitations and the most limiting factor is the small or restricted energy of the batteries in a wireless network. This is because of the assumption that mesh nodes that are deployed in urban areas tend to have no energy constraints while WMN nodes deployed in rural faces serious energy challenges. The latter relies on batteries and not on electricity supply which powers the WMN nodes in urban areas. This work, therefore, explores further the current trends towards maximising the network lifetime for the energy constrained networks. Hence the goal of this study is to design a path selection algorithm that is energyaware and optimising for the IEEE 802.11s based HWMP. The main idea is that paths with enough energy for transmission must be selected when transmitting packets in the network. Therefore, a simulation using NS-2 was carried out to assess the network performance of the proposed EAPM metric with the other metrics that have been analysed in literature including ETX. ETX has been used in WMNs but was not developed specifically for mesh. In conclusion, EAPM conserves more energy than the Multimetric, airtime link metric and lastly ETX. The simulation experiments show that EAPM optimises the energy used in the network and as a result EAPM has a prolonged network lifespan when comparing it to the rest of the metrics evaluated in this study. The results also revealed that the newly proposed EAPM exhibits superior performance characteristics even with regard to issues like end-to-end delay and packet delivery ratio. / CSIR Meraka Institute