Extended Hubbard model for mesoscopic transport in donor arrays in silicon

Arrays of dopants in silicon are promising platforms for the quantum simulation of the Fermi-Hubbard model. We show that the simplest model with only on-site interaction is insufficient to describe the physics of an array of phosphorous donors in silicon due to the strong intersite interaction in the system. We also study the resonant tunneling transport in the array at low temperature as a mean of probing the features of the Hubbard physics, such as the Hubbard bands and the Mott gap. Two mechanisms of localization which suppresses transport in the array are investigated: The first arises from the electron-ion core attraction and is significant at low filling; the second is due to the sharp oscillation in the tunnel coupling caused by the intervalley interference of the donor electron's wavefunction. This disorder in the tunnel coupling leads to a steep exponential decay of conductance with channel length in one-dimensional arrays, but its effect is less prominent in two-dimensional ones. Hence, it is possible to observe resonant tunneling transport in a relatively large array in two dimensions

Application of Optical Analyses to Cancer Therapeutics and Diagnostics

The extreme diversity and heterogeneity of cancer cells creates a need for equally varying analysis methods to diagnose and treat the disease. Many methods have been developed for targeting and combatting a specific cancer. The oestrogen receptor, HER2, is overexpressed in certain varieties of breast cancer and subsequently used as a target for chemotherapy antibody treatments. 1 Unfortunately, not all cancers overexpress an easily identifiable protein and are therefore limited to systemic, non-targeted therapies such as resection, radiation, and chemotherapy. 2 Here, three novel techniques are investigated for analysing cancer therapeutic and diagnostic techniques. Porous silicon microparticle (PSM) delivery methods take advantage of tumour vessel tortuosity and fenestrations to selectively deliver cancer therapeutics to tumours. In chapter 2, the previously uncharacterized rolling mechanics of PSM on endothelial cells are examined at physiologically relevant shear rates. Custom analysis software allows for the identification, tracking, and characterization of particles in flow. Tertiary lymphoid structures (TLS) in and around tumours have been prominently associated with positive patient prognoses but are difficult and time consuming to identify. In chapter 3, optical tissue clearing and 3D imaging are utilized to investigate the ability of dendritic cell (DC) vaccines and checkpoint blockade therapies to affect tumour growth in association with TLS presence in the tumour. When treated with the DC vaccine or a combination with anti-PD1 treatments, tumour growth is severely inhibited. The 3D imaging and analysis was used to correlate the tumour growth inhibition with an increase in the concentration of intratumoural T cells and of TLS present in the tumour. Optical spectroscopic imaging of biological systems has important applications in medical diagnosis and biochemistry. However, the extrinsic fluorescence of staining molecules often masks the intrinsic vibrational signals of biomolecules. In chapter 4, simultaneous spectroscopic bioimaging and photostability analysis of rhodamine 6G stained red blood cells using both fluorescence and resonance Raman imaging in a single laser excitation experiment were performed. A corresponding data processing algorithm was developed to separate the two previously indistinguishable spectroscopic signals

Impact of Asylum on Receiving Countries

Whereas asylum seekers and the systems for adjudicating their claims to refugee status in developed countries have garnished considerable attention and, often, have been at the centre of political controversy, there has been relatively little research on their actual impact on receiving countries. This article discusses the factors that determine the impact of asylum, as distinct from other forms of migration, concluding that the number of asylum seekers, government policies and socioeconomic characteristics all determine the impact of asylum. Hence, the impacts of asylum can differ significantly from country to country. Even within the same country, one could expect to see varied impacts depending on the age, education and skill level of individual asylum seekers. The paper then examines the fiscal, economic, and social impacts of asylum, as well as its impact on foreign policy and national security. It concludes with an examination of the impact of developed countries? asylum policies on the protection of refugees in developing countries. When refugee protection has been weakened in economically strong states and asylum restrictions are perceived as burden shifting, international protection in the developing world where most refugees try to survive has been undercut.asylum, fiscal impact, economic impact, national security

Direction of the Play: The House of Blue Leaves

This project entailed the selection, background research and documentation, casting, direction, and post-production analysis of Canon City High School\u27s production of John Guare\u27s The House of Blue Leaves by Andrew Fisher. Documentation included research and analysis of the play and an evaluation of the play as a production vehicle for Canon City High School

REACTIVE GASES IN ELECTROTHERMAL ATOMISATION ATOMIC ABSORPTION SPECTROMETRY

Philips Scientific, York Street, Cambridg

Doctor of Philosophy

dissertationThe increasing demand for smaller, more efficient circuits has created a need for both digital and analog designs to scale down. Digital technologies have been successful in meeting this challenge, but analog circuits have lagged behind due to smaller transistor sizes having a disproportionate negative affect. Since many applications require small, low-power analog circuits, the trend has been to take advantage of digital's ability to scale by replacing as much of the analog circuitry as possible with digital counterparts. The results are known as \emph{digitally-intensive analog/mixed-signal} (AMS) circuits. Though such circuits have helped the scaling problem, they have further complicated verification. This dissertation improves on techniques for AMS property specifications, as well as, develops sound, efficient extensions to formal AMS verification methods. With the \emph{language for analog/mixed-signal properties} (LAMP), one has a simple intuitive language for specifying AMS properties. LAMP provides a more procedural method for describing properties that is more straightforward than temporal logic-like languages. However, LAMP is still a nascent language and is limited in the types of properties it is capable of describing. This dissertation extends LAMP by adding statements to ignore transient periods and be able to reset the property check when the environment conditions change. After specifying a property, one needs to verify that the circuit satisfies the property. An efficient method for formally verifying AMS circuits is to use the restricted polyhedral class of \emph{zones}. Zones have simple operations for exploring the reachable state space, but they are only applicable to circuit models that utilize constant rates. To extend zones to more general models, this dissertation provides the theory and implementation needed to soundly handle models with ranges of rates. As a second improvement to the state representation, this dissertation describes how octagons can be adapted to model checking AMS circuit models. Though zones have efficient algorithms, it comes at a cost of over-approximating the reachable state space. Octagons have similarly efficient algorithms while adding additional flexibility to reduce the necessary over-approximations. Finally, the full methodology described in this dissertation is demonstrated on two examples. The first example is a switched capacitor integrator that has been studied in the context of transforming the original formal model to use only single rate assignments. Th property of not saturating is written in LAMP, the circuit is learned, and the property is checked against a faulty and correct circuit. In addition, it is shown that the zone extension, and its implementation with octagons, recovers all previous conclusions with the switched capacitor integrator without the need to translate the model. In particular, the method applies generally to all the models produced and does not require the soundness check needed by the translational approach to accept positive verification results. As a second example, the full tool flow is demonstrated on a digital C-element that is driven by a pair of RC networks, creating an AMS circuit. The RC networks are chosen so that the inputs to the C-element are ordered. LAMP is used to codify this behavior and it is verified that the input signals change in the correct order for the provided SPICE simulation traces

Effects of Temporal and Spatial Context Within the Macaque Face-Processing System

Temporal and spatial context play a key role in vision as a whole, and in face perception specifically. However, little is known about the neurophysiological mechanisms by which contextual cues exert their effects. Anatomically distinct face patches in the macaque brain analyze facial form, and studies of the activity within these patches have begun to clarify the neural machinery that underlies facial perception. This system provides a uniquely valuable opportunity to study how context affects the perception of form. We used functional magnetic resonance imaging (fMRI) to investigate the brain activity of macaque monkeys while they viewed faces placed in either temporal or spatial context. Facial motion transmits rich and ethologically vital information, but the way that the brain interprets such natural temporal context is poorly understood. Facial motion activates the face patches and surrounding areas, yet it is not known whether this motion is processed by its own specialized neural machinery, and if so, what that machinery’s organization might be. To address these questions, we monitored the brain activity of macaque monkeys while they viewed low- and high-level motion and form stimuli. We found that, beyond classical motion areas and the known face patch system, moving faces recruited a heretofore-unrecognized face patch. Although all face patches displayed distinctive selectivity for face motion over object motion, only two face patches preferred naturally moving faces, while three others preferred randomized, rapidly varying sequences of facial form. This functional divide was anatomically specific, segregating dorsal from ventral face patches, thereby revealing a new organizational principle of the macaque face-processing system. Like facial motion, bodies can provide valuable social context, revealing emotion and identity. Little is known about the joint processing of faces and bodies, even though there is reason to believe that their neural representations are intertwined. To identify interaction between the neural representations of face and body, we monitored the brain activity of the same monkeys while they viewed pictures of whole monkeys, isolated monkey heads, and isolated monkey bodies. We found that certain areas, including anterior face patches, responded more to whole monkeys than would be predicted by summing the separate responses to isolated heads and isolated bodies. The supralinear response was specific to viewing the conjunction of head and body; heads placed atop nonbody objects did not evoke this activity signature. However, a supralinear context response was elicited by pixelated, ambiguous faces presented on bodies. The size of this response suggests that the supralinear signal in this case did not result from the disambiguation of the ambiguous faces. These studies of contextually evoked activity within the macaque face processing system deepen our understanding of the cortical organization of both visual context and face processing, and identify promising sites for future research into the mechanisms underlying these critical aspects of perception

Supersymmetric gauge theories and their supercurrents

Using the method of dimensional reduction of N=l supersymmetric Yang-Mills theories from higher dimensions down to four dimensions, all possible supersymmetric Yang-Mills theories in four dimensions are obtained. The conserved currents associated with the symmetries of these models are then developed using Noether's theorem in ordinary space-time. By the variation of these conserved currents under supersymmetry transformations the supercurrent multiplets for the different models are obtained. Supersymmetric gauge theories are then discussed in superspace where differential geometry can be used to obtain Bianchi identities for the supersymmetric field strengths. The constraints on the field strengths that give rise to off-shell representations for each of the different supersymmetric gauge theories are then obtained and off-shell Lagrangians written down. The connection with supersymmetric gauge theories in ordinary space-time is made. The supercurrents in superspace are then derived using the generalization of Noether's theorem to superspace