Since wireless sensor networks are energy constrained, introducing a method that facilitates the efficient use of the available energy in each node is a fundamental design issue. In this work, a mechanism to monitor the residual energy of sensor networks is proposed. The information about the residual energy of each sensor node in the network is saved in a special node called monitoring node. This information can be used as input to other applications to prolong the network lifetime. Each sensor node in the network uses the proposed prediction-based model to forecast its energy consumption rate. The model's performance is measured based on the number of energy packets sent to the monitoring node for various thresholds (prediction errors). The simulation results showed that reducing the threshold will produce more accurate projection of the residual energy of each node in the monitoring node. However, as the threshold is further decreased the number of energy packets sent to the monitoring node grows significantly. This incurs higher energy map construction cost on the network in terms of energy and bandwidth. The simulation results also showed the tradeoff between increasing the accuracy of the prediction model and reducing the cost of energy map construction.

In this thesis, a pass-transistor logic synthesizer is developed for logic mapping of any combinational circuits based on only two types of cells: 2-to-1 multiplexors and inverters. The input contains several sum-of-product Boolean function expressions. Our synthesizer will consider the hardware sharing among these Boolean functions in order to save area. The output of our synthesizer is pass-transistor-based circuits with optimized transistor width in terms of user-specified speed and power performance measurement. During optimization, the Elmore RC delay model is used to estimate the critical path delay and the power is characterized by the switching of all the internal nodes. The final outputs are HSPICE netlists and Verilog gate-level code that allow more detailed timing simulation and automatic placement-routing.

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A masters thesis focussing on achieving improvements in transmission reliability and energy efficiency for a battery-powered wireless sensor node on the edge of an industrial heterogeneous wireless network that consists predominantly of mains-powered nodes. A router-switching technique is proposed to allow the sensor node to make gains in transmission reliability and energy efficiency by taking advantage of the scenario where multiple wireless routers are in range and switching between them, instead of only being able to transmit to one router. The research involves simulation of a number of network scenarios where the router-switching technique is enabled and disabled, to measure the advantage gained for the sensor in terms of its functional lifetime. The simulation is based on an abstract model that focusses on the edge of the mains-powered area of the network, where the battery-powered sensor is located. The simulation results show that for many cases, router-switching provides a higher level of transmission reliability and lower levels of energy consumption than the scenario where router-switching is disabled, as well as improvements in data loss rates.

T-lymphocytes (T-cells) trafficking in the lymph nodes (LNs) is key for T-cells activation and their effector functions in adaptive immune responses. T-cells enter the LNs through high endothelial venules (HEVs) and interact with dendritic cells (DCs) for cognate antigens in the T-cell zone (TCZ). After scanning the TCZ for antigens, T-cells leave the LNs through efferent lymphatic vessel. CCR7 and its ligands, CCL19 and CCL21 are involved in the recruitment and compartmentalization of T-cells in LNs. However, their specific role(s) in mediating T-cells migration in LNs sub-regions remain unclear. In addition, the mechanism behind the passage of T-cells from the TCZ to the abluminal side of medullary sinuses (for their exit through medullary sinuses) is not well understood. Here, I hypothesize that different CCL19 and CCL21 fields in LNs sub-regions, orchestrate T-cells sub-regional migration in LNs.. In this study, I examined the CCL19 and CCL21 distribution profiles in mouse LNs sub-regions by immunofluoroscence staining and confocal microscopy. Using microfluidic devices that can flexibly configure well-defined single and co-existing chemical concentration gradients, I quantitatively analyzed the migration of activated human blood T-cells in LNs relevant CCL19 and CCL21 fields. The results suggested a novel CCL19 and CCL21 based combinatorial guiding mechanism for T-cells migration in different LNs sub-regions. In particular, this mechanism operates in the TCZ periphery region to guide T-cells migration away from the TCZ. Furthermore, the CCL19 and CCL21 fields mimicking the region beyond the TCZ toward the medulla result in disturbed chemotaxis, which prevents T-cells from being attracted back to the TCZ. Taken together, this microfluidics-based in vitro study shows the coordinated T-cells migration in different single and combined CCL19 and CCL21 fields, leading to interesting new insights into the guiding mechanisms for T-cells trafficking in LNs sub-regions.

Network design problems involving survivability usually include trade-off of the potential for lost revenues and customer goodwill against the extra costs required to increase the network survivability. It also involves selection of nodes and edges from lists of potential sets to accomplish certain desirable properties. In many applications it is imperative to have built-in reliability or survivability of the network. Delays of traffic are undesirable since it affects quality of service (QoS) to clients of the network. In this dissertation we consider the construction of an optimization system for network design with survivability properties that may help in the planning of mesh topologies while maintaining a certain degree of survivability of the network. This is done by providing for at least two diverse paths between certain "special" nodes to provide protection against any single edge or node failure. This part is modelled by using mixed integer programming techniques. A software product called CPLEX then solves these models and various facilities are built into the decision support system to allow the decision maker to experiment with some topological and flow requirement changes. / Thesis (M.Sc. (Computer Science))--North-West University, Potchefstroom Campus, 2007

Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2005. / Vita. Includes bibliographical references (leaves 156-169).

Introduction: Factors that influence atrioventricular (AV) nodal conduction are complex and not well understood. Multiple studies have been performed to explain the mechanisms responsible for AV nodal conduction but the AV node (AVN) remains a "riddle". With ageing there is an increase in the incidence of AV nodal dysfunction leading to AV block. Methodology: I have performed electrophysiological (EP) and immunohistochemistry experiments on male Wistar-Hanover rats aged 3 months (equivalent to 20 year old humans; n=24) and 2 years (equivalent to 70 year old humans; n=15). AH interval, Wenkebach cycle length (WCL) and AV node effective refractory period (AVNERP) were measured. I used cesium (Cs+ = 2 mM) to block HCN channels responsible for the funny current "If " (and therefore the membrane clock), and ryanodine (2 μM) to block RyR2 channels responsible for Ca2+ release from the sarcoplasmic reticulum (and therefore the Ca2+ clock) in the two age groups. Protein expression in each group (from n=9 young and n=8 old rats) from different regions of the AV conduction axis: inferior nodal extension (INE), compact node (CN), proximal penetrating bundle (PPB) and distal penetrating or His bundle (His) were studied using immunofluorescence and confocal microscopy. The expression of the gap junction channels Cx43 and Cx40 and ion channel’s including HCN4 (responsible for If current), Nav1.5 (major cardiac Na+ channel responsible for INa) and Cav1.3 (L-type Ca2+ channel), and calcium handling proteins, RyR2 and SERCA 2a (involved in Ca2+ release and reuptake from cardiac sarcoplasmic reticulum, SR) were studied. Semi-quantitative signal intensity of these channels was measured using Volocity software. Structural characteristics of the tissue were studied using histology (Masson’s trichome stain and picrosirius red stain for collagen). Statistical analysis was performed with Prism 6.0. Electrophysiological measurements were performed using Spike2.Results: Without drugs to block the If current and Ca2+ release from the SR, there was a significant prolongation of the AH interval (P<0.005), WCL (P<0.005) and AVNERP (P<0.001) with ageing. In young rats (but not old rats), Cs+ prolonged the AH interval (P<0.001), WCL (P<0.01) and AVNERP (P<0.01). Ryanodine prolonged the AH interval (P<0.01) and WCL (P<0.01) in young and old rats. Immunofluorescence revealed that with ageing: Cx43 is downregulated in the PPB and His (P<0.05); Cx40 is upregulated in the INE and CN (P<0.05); HCN4 is downregulated in the His bundle (P=0.05); Nav1.5 is downregulated in the CN and PB (P<0.05); RyR2 is downregulated in the CN and PPB (P<0.05); SERCA2a and Cav1.3 is upregulated in the PPB (P<0.05). Histology confirmed that with ageing that the cells of CN, PPB and His are more loosely packed and irregularly arranged. There is cellular hypertrophy, decrease in the number of nuclei and increase in the collagen content with ageing. The clinical study has shown that elderly patients with syncope and cardiac conduction system disease are at risk of high mortality and recurrent transient loss of consciousness. Conclusion: For the first time, we have shown that both HCN and RyR2 channels play an important role in AV nodal conduction. With ageing the expression of HCN4 and the role of If in AV nodal conduction decreases, whereas the role of Ca2+ clock in AV nodal conduction was unchanged, although the expression of RyR2 and SERCA2a changes. The clinical study suggests that AV nodal disease is associated with significant morbidity and higher mortality among elderly patients who present with transient loss of consciousness.

In an urban context, architecture and landscape architecture co-exist as part of the structure of the city. In the same manner, interior architecture exists as part of an architectural envelope, and product design as an integral part of the interior. This study explores the relationship between these design disciplines and their interdependence; none of them can be practiced optimally in isolation. As this thesis deals with interior architecture, the influence of and the response to other fields of design are considered and investigated, setting the parameters for the resolution of the design framework. The objective of the thesis is to design a tourism and information centre for Tshwane. The shortcomings of the tourism industry in the city are identified in Chapter Two, and the tourism field studied in depth in Chapter Three. The conclusions from these chapters serve as generators for the functional design process. The site of the Old Fire Station Building was chosen for both its potential and its inadequacies. Its physical attributes, historical importance and its critical role in the urban context of the CBD and the Museum Park District are discussed in Chapter Four. Chapter Five deals with the design philosophy and approach to creating a successful public space. Precedents are analytically examined in Chapter Six and alternatives are explored, setting up requirements and guidelines for the design intervention. In Chapter Seven, design strategies are defined and consequently employed. The progression of the design from general concept to specific end product is illustrated visually. Attention is focused on two parts of the building: the information area (Portion A) and the café (Portion B). In Chapter Eight, Portion A is further developed on a technical and tectonic level, zooming in on the construction of the information reception box. The study concludes with the technical documentation contained in Chapter Nine. The study relies throughout on the application of the concepts of placemaking through the layering, defining and containing of space, and contrast the existing with the proposed intervention. / Dissertation (MInt(Prof))--University of Pretoria, 2008. / Architecture / unrestricted

Histopathology of a murine lymph node, 9 days post infection with Coccidioides. Magnification 10X