The Opportunity Cost of Violence: An Analysis of the Relationship Between Foreign Aid and Terrorism in Sub-Saharan Africa

Senior Project submitted to The Division of Social Studies of Bard College

Efficient planar camera calibration via automatic image selection

This paper details a novel approach to automatically selecting images which improve camera calibration results. An algorithm is presented which identifies calibration images that inherently improve camera parameter estimates based on their geometric configuration or image network geometry. Analysing images in a more intuitive geometric framework allows image networks to be formed based on the relationship between their world to image homographies. Geometrically, it is equivalent to enforcing maximum independence between calibration images, this ensures accuracy and stability when solving the planar calibration equations. A webcam application using the proposed strategy is presented. This demonstrates that careful consideration of image network geometry, which has largely been neglected within the community, can yield more accurate parameter estimates with less images

Generalising the ideal pinhole model to multi-pupil imaging for depth recovery

This thesis investigates the applicability of computer vision camera models in recovering depth information from images, and presents a novel camera model incorporating a modified pupil plane capable of performing this task accurately from a single image. Standard models, such as the ideal pinhole, suffer a loss of depth information when projecting from the world to an image plane. Recovery of this data enables reconstruction of the original scene as well as object and 3D motion reconstruction. The major contributions of this thesis are the complete characterisation of the ideal pinhole model calibration and the development of a new multi-pupil imaging model which enables depth recovery. A comprehensive analysis of the calibration sensitivity of the ideal pinhole model is presented along with a novel method of capturing calibration images which avoid singularities in image space. Experimentation reveals a higher degree of accuracy using the new calibration images. A novel camera model employing multiple pupils is proposed which, in contrast to the ideal pinhole model, recovers scene depth. The accuracy of the multi-pupil model is demonstrated and validated through rigorous experimentation. An integral property of any camera model is the location of its pupil. To this end, the new model is expanded by generalising the location of the multi-pupil plane, thus enabling superior flexibility over traditional camera models which are confined to positioning the pupil plane to negate particular aberrations in the lens. A key step in the development of the multi-pupil model is the treatment of optical aberrations in the imaging system. The unconstrained location and configuration of the pupil plane enables the determination of optical distortions in the multi-pupil imaging model. A calibration algorithm is proposed which corrects for the optical aberrations. This allows the multi-pupil model to be applied to a multitude of imaging systems regardless of the optical quality of the lens. Experimentation validates the multi-pupil model’s accuracy in accounting for the aberrations and estimating accurate depth information from a single image. Results for object reconstruction are presented establishing the capabilities of the proposed multi-pupil imaging model

Posterior Uncertainty Estimation via a Monte Carlo Procedure Specialized for Data Assimilation

Through the Bayesian lens of data assimilation, uncertainty on model parameters is traditionally quantified through the posterior covariance matrix. However, in modern settings involving high-dimensional and computationally expensive forward models, posterior covariance knowledge must be relaxed to deterministic or stochastic approximations. In the carbon flux inversion literature, Chevallier et al. proposed a stochastic method capable of approximating posterior variances of linear functionals of the model parameters that is particularly well-suited for large-scale Earth-system data assimilation tasks. This note formalizes this algorithm and clarifies its properties. We provide a formal statement of the algorithm, demonstrate why it converges to the desired posterior variance quantity of interest, and provide additional uncertainty quantification allowing incorporation of the Monte Carlo sampling uncertainty into the method's Bayesian credible intervals. The methodology is demonstrated using toy simulations and a realistic carbon flux inversion observing system simulation experiment

MANIPULATING TIME: DIFFERENCES IN PEAK KNEE MOMENTS WHEN SIDESTEPPING TO TEMPORALLY CONSTRAINED QUASI-REALISTIC SCENARIOS

This study aimed to analyse how planning time effects peak knee valgus (PKVM) and internal rotation (PKIRM) moments using real-time (RT) and above real-time (ART) game-like video clips. 12 male Australian rules football players completed a modified sidestepping (SS) movement assessment. PKVM and PKIRM were measured across the weight acceptance phase of planned (PSS) and four unplanned SS conditions, increasing in video playback speed (UP100, UP125, UP150, UP175). No significant differences were found for PKVM or PKIRM between any SS conditions, however, the coefficient of variation in PKVM increased as the temporal constraints of the unplanned tasks increase. This study suggests that while mean group differences in PKVM may not be obvious, increased individual subject variation is evident as planning time decreases

Cell Death Pathways in Directly Irradiated Cells and Cells Exposed to Medium from Irradiated Cells

Purpose: The aim of this study was to compare levels of apoptosis, necrosis, mitotic cell death and senescence after treatment with both direct radiation and irradiated cell conditioned medium. Materials and methods: Human keratinocytes (HaCaT cell line) were irradiated (0.005, 0.05 and 0.5 Gy) using a cobalt 60 teletherapy unit. For bystander experiments, the medium was harvested from donor HaCaT cells one hour after irradiation and transferred to recipient HaCaT cells. Clonogenic assay, apoptosis, necrosis, mitotic cell death, senescence and cell cycle analysis were measured in both directly irradiated cells and bystander cells Results: A reduction in cell survival was observed for both directly irradiated cells and irradiated cell conditioned medium (ICCM) treated cells. Early apoptosis and necrosis was observed predominantly after direct irradiation. An increase in the number of cells in G2/M phase was observed at 6 and 12 hours which led to mitotic cell death after 72 hours following direct irradiation and ICCM treatment. No senescence was observed in the HaCaT cell line following either direct irradiation or treatment with ICCM. Conclusion: This study has shown that directly irradiated cells undergo apoptosis, necrosis and mitotic cell death whereas ICCM treated cells predominantly undergo mitotic cell deat

PELVIC OBLIQUITY AND ROTATION INFLUENCES FOOT POSITION ESTIMATES DURING RUNNING AND SIDESTEPPING: “IT’S ALL IN THE HIPS”

Pelvic obliquity angles were hypothesised to influence mediolateral (ML) foot position estimates during sporting manoeuvres. Pelvic angles and ML foot position estimates during the weight acceptance phase of sidestepping and straight-line running tasks were obtained from 31 amateur Australian Rules Football players using three different kinematic models. ML foot position was calculated: 1) in the global reference frame, 2) in the pelvis reference frame and 3) in the pelvis reference frame following correction for changes in pelvic obliquity. Significant differences in ML foot position were observed between all three models in both task conditions (p \u3c 0.05). Correcting for changes in time varying pelvic obliquity during running and sidestepping tasks is an important modelling consideration for the reliable measurement of ML foot position when investigating injury and/or stability

Reactive Oxygen Species and Nitric Oxide Signaling in Bystander Cells

It is now well accepted that radiation induced bystander effects can occur in cells exposed to media from irradiated cells. The aim of this study was to follow the bystander cells in real time following addition of media from irradiated cells and to determine the effect of inhibiting these signals. A human keratinocyte cell line, HaCaT cells, was irradiated (0.005, 0.05 and 0.5 Gy) with γ irradiation, conditioned medium was harvested after one hour and added to recipient bystander cells. Reactive oxygen species, nitric oxide, Glutathione levels, caspase activation, cytotoxicity and cell viability was measured after the addition of irradiated cell conditioned media to bystander cells. Reactive oxygen species and nitric oxide levels in bystander cells treated with 0.5Gy ICCM were analysed in real time using time lapse fluorescence microscopy. The levels of reactive oxygen species were also measured in real time after the addition of extracellular signal-regulated kinase and c-Jun amino-terminal kinase pathway inhibitors. ROS and glutathione levels were observed to increase after the addition of irradiated cell conditioned media (0.005, 0.05 and 0.5 Gy ICCM). Caspase activation was found to increase 4 hours after irradiated cell conditioned media treatment (0.005, 0.05 and 0.5 Gy ICCM) and this increase was observed up to 8 hours and there after a reduction in caspase activation was observed. A decrease in cell viability was observed but no major change in cytotoxicity was found in HaCaT cells after treatment with irradiated cell conditioned media (0.005, 0.05 and 0.5 Gy ICCM). This study involved the identification of key signaling molecules such as reactive oxygen species, nitric oxide, glutathione and caspases generated in bystander cells. These results suggest a clear connection between reactive oxygen species and cell survival pathways with persistent production of reactive oxygen species and nitric oxide in bystander cells following exposure to irradiated cell conditioned media