Engineered nanostructures for metal enhanced fluorescence applications in the near-infrared

Recent advancements in fabrication techniques allow construction of nanostructures with well-defined features in nanometres scale. Tiny nanostructures that have features below the resolution of optical diffraction limit can now be made in the laboratory. The specific properties of those nanostructures with specific properties made from variety of materials allow us to study and explore many different properties that have never been observed while they are in bulk. One such phenomenon is localised surface plasmon resonance effect, which is exhibited by certain materials when in nanometric size. Their peculiar interaction with light is in such a way that the optical properties such as reflection and transmission deviate from typical characteristics and change according to the material involved and their shapes. Furthermore, this effect could also enhance the electric field in a specific area of the structure. This thesis is motivated by the attractiveness of the tunability of localised surface plasmon resonance and aims at exploring those properties by fabricating multiple types of nanostructures through a low-cost and versatile technique called nanosphere lithography. By improving the technique and combining with other fabrication techniques (such as oxygen plasma etching and argon ion milling), a large variety of nanostructures with hexagonal lattice like as nanocones, nanopencils, and nanofins arrays have been successfully created. Among them, three main types of nanostructure were selected for detailed study: nanotriangle, nanodisc, and nanohole-disc arrays. The distance between the adjacent nanoparticles were changed in those structures and strong interparticle coupling behaviours were observed as the distance between them becomes shorter. Current portable biosensing devices for in vitro studies are limited by the sensitivity limit of the detector, the poor quality of emitters and the size of the devices. In this thesis, the application of localised surface plasmon resonance for near infrared in vitro biosensing is explored. This is achieved through a mechanism called metal enhanced fluorescence. The techniques take advantage of the high electrical field strength and the resonance condition of the plasmon to enable a fluorophore to achieve brighter emission. The greater the resonance and electrical field are, the greater the emission amplification would be. Such effect makes it highly attractive for near infrared in vitro studies, which benefits from high optical penetration of common biology components such as water and lipids, but suffer from poor emission of existing fluorophores. Thus, enhancement of the emission signals through metal enhance fluorescence mechanism is an attractive route to obtain better signal to noise ratio in medical diagnostic, and improve detectability while at the same time reduce the need of a high sensitivity detector which can be costly and large in size. The three chosen nanostructures, i.e. nanotriangular arrays, nanodisc arrays and nanohole-disc arrays have shown marked enhancement in the emission of attached fluorophores up to 83x, 235x, and 411x respectively, making them highly attractive nanostructures for such application.Open Acces

Pursuit-Evasion with Acceleration, Sensing Limitation, and Electronic Counter Measures

Abstract: The use of game theory to analyze the optimal behaviors of both pursuers and evaders originated with Isaac\u27s work at the Rand Corporation in the 1950\u27s. Although many variations of this problem have been considered, published work to date is limited to the case where both players have constant velocities. In this thesis, we extend previous work by allowing players to accelerate. Analysis of this new problem using Newton\u27s laws imposes an additional constraint to the system, which is the relationship between players\u27 velocities and allowed turning radius. We find that analysis of this relationship provides new insight into the evader capture criteria for the constant velocity case. We summarize our results in a flow chart that expresses the parameter values that determine both the games of kind and games of degree associated with this problem. Pursuit-evasion games in the literature typically either assume both players have perfect knowledge of the opponent\u27s position, or use primitive sensing models. These unrealistically skew the problem in favor of the pursuer who need only maintain a faster velocity at all turning radii. In real life, an evader usually escapes when the pursuer no longer knows the evader\u27s position. We analyze the pursuit-evasion problem using a realistic sensor model and information theory to compute game theoretic payoff matrices. Our results show that this problem can be modeled as a two-person bi-matrix game. This game has a saddle point when the evader uses strategies that exploit sensor limitations, while the pursuer relies on strategies that ignore sensing limitations. Later we consider for the first time the effect of many types of electronic counter measures (ECM) on pursuit evasion games. The evader\u27s decision to initiate its ECM is modeled as a function of the distance between the players. Simulations show how to find optimal strategies for ECM use when initial conditions are known. We also discuss the effectiveness of different ECM technologies in pursuit-evasion games

Most robust and fragile two-qubit entangled states under depolarizing channels

For a two-qubit system under local depolarizing channels, the most robust and most fragile states are derived for a given concurrence or negativity. For the one-sided channel, the pure states are proved to be the most robust ones, with the aid of the evolution equation for entanglement given by Konrad et al. [Nat. Phys. 4, 99 (2008)]. Based on a generalization of the evolution equation for entanglement, we classify the ansatz states in our investigation by the amount of robustness, and consequently derive the most fragile states. For the two-sided channel, the pure states are the most robust for a fixed concurrence. Under the uniform channel, the most fragile states have the minimal negativity when the concurrence is given in the region [1/2,1]. For a given negativity, the most robust states are the ones with the maximal concurrence, and the most fragile ones are the pure states with minimum of concurrence. When the entanglement approaches zero, the most fragile states under general nonuniform channels tend to the ones in the uniform channel. Influences on robustness by entanglement, degree of mixture, and asymmetry between the two qubits are discussed through numerical calculations. It turns out that the concurrence and negativity are major factors for the robustness. When they are fixed, the impact of the mixedness becomes obvious. In the nonuniform channels, the most fragile states are closely correlated with the asymmetry, while the most robust ones with the degree of mixture.Comment: 10 pages, 9 figs. to appear in Quantum Information & Computation (QIC

Generalized Variational Oscillation Principles for Second-Order Differential Equations with Mixed-Nonlinearities

Using generalized variational principle and Riccati technique, new oscillation criteria are established for forced second-order differential equation with mixed nonlinearities, which improve and generalize some recent papers in the literature

Impact of Chinese small business on sustainable livelihoods in Port Elizabeth after 1994

Since the advent of democracy in April 1994, the issues of economic empowerment and growth have been high on the agenda of the Government of National Unity of South Africa. In order to achieve social-economic growth, resolve wealth and asset gaps between rich and poor, decrease unemployment and meet the Millennium Development Goals, government has sought efficient mechanisms of transformation. The formation of SMMEs was put forward as a solution to solve the above problems. SMMEs play a vital role in economic development and livelihoods uplifting. The purpose of this study is to examine how Chinese SMMEs have impacted on sustainable livelihoods in Nelson Mandela Bay Metropolitan District. The study has identified the challenges of local livelihoods in the district. The findings on the effects of Chinese SMMEs were that: (1) They have provided affordable goods and services to local people, improving livelihoods by means of reducing living costs of the local population and thus providing relief on their financial capital; (2) The vast extent of their services in the district has enlarged their network of offerings in urban, suburban and even rural settings; (3) They have enabled the poor’s access to the economic markets and services; (4) They have contributed positively to employment by providing local jobseekers with gainful employment and access to financial capital; (5) They have empowered the local employee base through training and skills transfer; (6) They have promoted knowledge and skills that have enriched local human capital and positively contributed to livelihoods; and (7) They have made a contribution to GDP and tax revenues. Revenues fed to government have helped fund welfare and public services, including in the areas of education, health care, pensions, unemployment benefits, public transportation, infrastructure and housing. These benefits have collectively contributed to the improvement of local livelihoods in the district

Performance evaluation of Compass dual-mode receiver

Recently, navigation technology based on satellite navigation system has got more and more attention in international society because of its great values for both military and civil application. While navigation signal simulator which can generate satellite navigation signals and simulate different scenarios, not only satisfy cooperating test requirements of ground operation control system, test of the signal receivers, but also been playing a very important role in the development, test and evaluation of different navigation receiver, such as radio determination satellite system (RDSS) receiver, radio navigation satellite system (RNSS) receiver and dual-mode receivers. It is an indispensable tool for the design of the receivers．Compared to other satellite navigation systems, such as Global Positioning System (GPS) and GLobal Navigation Satellite System (GLONASS), BeiDou Navigation Satellite System (Compass/BDS) have some different unique characteristics, especially in RDSS determination. Firstly, the principle of comprehensive RDSS position and report is presented. Then function architecture of Compass signal simulator and requirements of the dynamic navigation signal simulation are analyzed. Finally, two key mathematical models are established to simulate the signals arriving at the receiver antenna for dual-mode receiver test, which are: the transmitting time iterative model and efficient satellite orbit approximation model. The results show that the Compass dual-mode simulator can satisfy dual-mode receiver’s test requirements