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The New Economic Geography literature has experienced an impressive success in economic theory. At the same time, the empirical evidence about the forces and mechanisms emphasized by this literature is growing. Nevertheless, there is still much to be gained from empirical analysis. The main objective of this work is thus to help mind this gap by providing further evidence on the relevance of agglomeration forces for the distribution of economic activities. We address this task from an eclectic perspective using both descriptive and structural approaches. We also pay particular attention to plants' heterogeneity and its interaction with spatial externalities. Our results are consistent with the hypothesis that pecuniary externalities stemming from final consumption and input-output linkages play an important role in location choice. Furthermore, while big plants are more sensitive to very localized externalities, small units display a stronger spatial correlation pattern and can be found more easily close to big consumers' markets.

The New Economic Geography literature has experienced an impressive success in economic theory. At the same time, the empirical evidence about the forces and mechanisms emphasized by this literature is growing. Nevertheless, there is still much to be gained from empirical analysis. The main objective of this work is thus to help mind this gap by providing further evidence on the relevance of agglomeration forces for the distribution of economic activities. We address this task from an eclectic perspective using both descriptive and structural approaches. We also pay particular attention to plants' heterogeneity and its interaction with spatial externalities. Our results are consistent with the hypothesis that pecuniary externalities stemming from final consumption and input-output linkages play an important role in location choice. Furthermore, while big plants are more sensitive to very localized externalities, small units display a stronger spatial correlation pattern and can be found more easily close to big consumers' markets.

Vehicular ad hoc networks (VANETs) have attracted much attention over the last few years. VANETs own several significant characteristics, such as the high-rate changing topology led by velocity of vehicles, time-and-location critical safety applications, and Global Positioning System (GPS) devices. In VANETs, as vehicle movement is usually restricted in just bidirectional movements along the roads and streets, geographical location information becomes very useful. In addition, many studies show that position-based routing protocol is a more promising routing strategy for VANETs; therefore security and verification of location information are necessary to be researched. In this thesis, a location verification approach, namely the Cooperative Location Verification (CLV) protocol, is proposed, aiming to prevent position-spoofing attacks on VANETs. The CLV basically uses two vehicles, a Verifier and a Cooperator, to verify the claimed position of a vehicle (Prover), according to two challenge-response procedures. Additionally, the security analysis of the CLV is presented. In order to enhance the CLV by reduce the network overhead, a reputation management system is designed. It utilizes the verification results of the CLV application and maintain every vehicle's reliability in the network. In addition, the solution to sparse networks is briefly discussed. In the simulation, the results show that the proposed CLV performs better than another location verification algorithm, namely the Secure Location Verification (SLV). And the effectiveness of the reputation management system is also demonstrated.

The purpose of this thesis is to analyze a non-intrusive connectivity visualization method for OLSR-based MANET topology in different mobility models. The visualization relies on the local topology databases (neighborhood database and topology database) available in OLSR nodes in the network. Two different views are considered in this method: central view and nodal view. In the central view, the network topology is viewed from a control center which has access to the databases of all nodes, while on the other hand, the nodal visualization provides a picture of the network topology from individual nodes point of view. In this thesis, the full view of the network has been compared to the nodal view to calculate the error rate for topology discovery, based on the total numbers of active and undiscovered links. The main contribution of this thesis is to analyze and improve the accuracy of coarse localization techniques under different mobility models, using the Force-directed algorithm to calculate the approximate location of the nodes. The localization information was gathered from layer-3 connectivity, utilizing anchor nodes that are equipped with GPS and other non-GPS nodes instead of using traditional methods that include received signal strength, time of arrival and angle of arrival. The approximate location information of the nodes derived from this technique has been compared with original node location in order to determine the accuracy of this technique. To improve the accuracy, several mobility prediction filters such as moving average filter, Kalman filter and low pass filter have been applied to the approximate location data. The simulation is done to calculate the error between the original location data and the coarse approximations, and the results shows that Moving Average provides the best results. / UOIT

In the nervous system, the roles of Kv channels are well established as being critical for regulating action potential frequency, membrane potential, and neurotransmitter release. However, their role in glial cells, a non-excitable cell type, is yet to be fully understood. Whole-cell current kinetics, pharmacology, immunocytochemistry and RT-PCR were used to characterize A-type current in hippocampal astrocyte cultures to better understand its function. Pharmacological analysis suggests that ~70%, 10% and less than 5% of total A current is associated with Kv4, Kv3 and Kv1 channels, respectively. In addition, pharmacology and kinetics provide novel evidence for a significant contribution of KChIP accessory proteins to astrocytic A-channel composition. Localization of the Shaw Kv3.4 channel to astrocytic processes and the Shal Kv4.3 channel to soma suggest that these channels serve a specific function. Since astrocytes are known to be subjected to neuronal firing frequencies of up to 200 Hz in the hippocampus, the role of A currents in membrane voltage oscillations was assessed. Although TEA-sensitive delayed-rectifying currents are involved in the extent of repolarization, 4-AP-sensitive A currents serve to increase the rate. Astrocytes and HEK293 cells were used to investigate the mechanism of the previously found GABAA induced anion-mediated reduction of Kv channels in more detail. Astrocytes demonstrate an anion concentration specific depolarizing effect on inactivating A-type (also termed transient voltage-gated) K+ channel activation kinetics whereas a hyperpolarizing effect was seen upon expression of Kv4.2 or Kv1.4 in HEK293 cells, but only after disruption of the cytoskeleton using cytochalasin D. It is hypothesized that cytoskeletal interactions and Cl -mediated effects are mediated through N-terminal conformational stabilities. <p>In summary, the results indicate that hippocampal astrocytes in vitro express multiple A type Kv channel á subunits with accessory, Ca2+-sensitive cytoplasmic subunits that appear to be specifically localized to subcellular membrane compartments. Functions of these channels remain to be determined in a physiological setting, but suggest that A-type Kv channels enable astrocytes to respond rapidly with membrane voltage oscillations to high frequency incoming signals, possibly synchronizing astrocyte function to neuronal activity. Furthermore, studies of anion and cytoskeletal effects on Kv channels demonstrate channel function to be highly localized/targeted and susceptible to changes in ionic environment.

In the nervous system, the roles of Kv channels are well established as being critical for regulating action potential frequency, membrane potential, and neurotransmitter release. However, their role in glial cells, a non-excitable cell type, is yet to be fully understood. Whole-cell current kinetics, pharmacology, immunocytochemistry and RT-PCR were used to characterize A-type current in hippocampal astrocyte cultures to better understand its function. Pharmacological analysis suggests that ~70%, 10% and less than 5% of total A current is associated with Kv4, Kv3 and Kv1 channels, respectively. In addition, pharmacology and kinetics provide novel evidence for a significant contribution of KChIP accessory proteins to astrocytic A-channel composition. Localization of the Shaw Kv3.4 channel to astrocytic processes and the Shal Kv4.3 channel to soma suggest that these channels serve a specific function. Since astrocytes are known to be subjected to neuronal firing frequencies of up to 200 Hz in the hippocampus, the role of A currents in membrane voltage oscillations was assessed. Although TEA-sensitive delayed-rectifying currents are involved in the extent of repolarization, 4-AP-sensitive A currents serve to increase the rate. Astrocytes and HEK293 cells were used to investigate the mechanism of the previously found GABAA induced anion-mediated reduction of Kv channels in more detail. Astrocytes demonstrate an anion concentration specific depolarizing effect on inactivating A-type (also termed transient voltage-gated) K+ channel activation kinetics whereas a hyperpolarizing effect was seen upon expression of Kv4.2 or Kv1.4 in HEK293 cells, but only after disruption of the cytoskeleton using cytochalasin D. It is hypothesized that cytoskeletal interactions and Cl -mediated effects are mediated through N-terminal conformational stabilities. <p>In summary, the results indicate that hippocampal astrocytes in vitro express multiple A type Kv channel á subunits with accessory, Ca2+-sensitive cytoplasmic subunits that appear to be specifically localized to subcellular membrane compartments. Functions of these channels remain to be determined in a physiological setting, but suggest that A-type Kv channels enable astrocytes to respond rapidly with membrane voltage oscillations to high frequency incoming signals, possibly synchronizing astrocyte function to neuronal activity. Furthermore, studies of anion and cytoskeletal effects on Kv channels demonstrate channel function to be highly localized/targeted and susceptible to changes in ionic environment.

Vehicular ad hoc networks (VANETs) have attracted much attention over the last few years. VANETs own several significant characteristics, such as the high-rate changing topology led by velocity of vehicles, time-and-location critical safety applications, and Global Positioning System (GPS) devices. In VANETs, as vehicle movement is usually restricted in just bidirectional movements along the roads and streets, geographical location information becomes very useful. In addition, many studies show that position-based routing protocol is a more promising routing strategy for VANETs; therefore security and verification of location information are necessary to be researched. In this thesis, a location verification approach, namely the Cooperative Location Verification (CLV) protocol, is proposed, aiming to prevent position-spoofing attacks on VANETs. The CLV basically uses two vehicles, a Verifier and a Cooperator, to verify the claimed position of a vehicle (Prover), according to two challenge-response procedures. Additionally, the security analysis of the CLV is presented. In order to enhance the CLV by reduce the network overhead, a reputation management system is designed. It utilizes the verification results of the CLV application and maintain every vehicle's reliability in the network. In addition, the solution to sparse networks is briefly discussed. In the simulation, the results show that the proposed CLV performs better than another location verification algorithm, namely the Secure Location Verification (SLV). And the effectiveness of the reputation management system is also demonstrated.

The increased market for navigation, localization and mapping system has encouraged the research to dig deeper into these new and challenging areas. The remarkable development of computer soft- and hardware have also opened up many new doors. Things which more or less where impossible ten years ago are now reality. The possibilities of using a mathematical approach to compensate for the need of expensive sensors has been one of the main objectives in this thesis. Here you will find the basic principles of localization of indoor UAVs using particle filter (PF) and Octomaps, but also the procedures of implementing 2D scanmatching algorithms and quaternions. The performance of the algorithms is evaluated using a high precision motion capture system. The UAV which forms the basis for this thesis is equipped with a 2D laser and an inertial measurement unit (IMU). The results show that it is possible to perform localization in 2D with centimetre precision only by using information from a laser and a predefined Octomap.

Peritrichously flagellated bacteria carry out chemotaxis by modulating the frequency of switching between smooth swimming and tumbling. The tumbling frequency is controlled by a signal transduction cascade in which transmembrane receptors modulate the activity of a histidine kinase CheA that transfers phosphate to its cognate response regulator CheY. The proteins of the chemotaxis signaling cascade are localized to clusters found primarily at the poles of cells. In this work, the localization of the CheZ protein, a phosphatase that dephosphorylates CheY~P, is examined. Using a CheZ-GFP fusion protein, we show that CheZ was localized to the polar receptor patch via interaction with the short form of CheA (CheAS). Aromatic residues of CheZ near one end of the elongated CheZ four-helix bundle were determined to be critical for localization. Aliphatic residues in CheAS were also determined to be critical for CheZ localization to the receptor patch and substitution of these residues conferred a tumble bias to swimming cells. A mechanism of CheZ localization is proposed in which the CheZ apical loop interacts with a binding site formed by dimerization of the P1 domain of CheAS. The potential role of CheZ localization as a means of coordinating the rotation state of peritrichously distributed flagella is discussed.