Giant cell arteritis: diagnostic prediction models, temporal artery biopsy and epidemiology

Giant cell arteritis (GCA) is the most common primary vasculitis in the elderly and can cause irreversible blindness, aortitis, and stroke. Diagnostic confirmation of GCA usually entails temporal artery biopsy (TABx) – a time-consuming and invasive test, or ultrasound. The primary treatment of GCA is with high dose glucocorticoids that have numerous potential side effects. Glucocorticoids are initiated prior to the TABx result, due to the risk of interim blindness. By 2050 the cost of blindness from GCA in the United States is estimated at $76 billion with an additional$6 billion from glucocorticoid-induced fractures. This thesis examines knowledge gaps in the diagnosis and epidemiology of GCA. Needed refinements in the diagnosis of GCA included: i) the optimization of diagnostic prediction models (PMs) and ii) clarification of the contemporary utilization parameters of TABx. With regards to i) previous PMs are usually based on limited sample size, do not leverage sufficient clinical predictors, or include continuous variables, and not compliant with the transparent reporting guidelines for diagnostic PMs (TRIPOD). Using multicentre data of consecutive patients undergoing TABx, the largest (n=1,201) and most comprehensive logistic regression and, neural network PMs for GCA were formulated. Age, platelet level, jaw claudication and vision loss eventuated as the key predictor variables. An online risk calculator was developed from the PM and could decrease both the number of ABx performed on low-risk patients, and the morbidity from unneeded glucocorticoids. Regarding ii) although TABx has long been acknowledged as the gold standard test for GCA the current preference for TABx versus ultrasound amongst neuro-ophthalmologists and the utility rate of TABx are unknown. The thesis survey revealed that 91% of neuroophthalmologists preferred TABx over ultrasound as the confirmatory test for GCA. The first systematic review for the utility rate of TABx disclosed a median positive yield of 25% and provides a benchmark for institutions performing this procedure. Knowledge gaps in the epidemiology of GCA important for public health planning included the incidence of GCA in Ontario, Canada, and the controversial role of herpes zoster in the development of GCA given the advent of zoster vaccines. Pathology audit and an assay of billing data revealed the incidence of biopsy-proven GCA in Ontario to be 4.9 per 100,000 individuals 50 years of age or older. On ecologic analysis, the inverse relationship of the incidence rates of herpes zoster versus GCA per country suggested zoster is not a major immunopathogenic trigger for GCA. In summary, this thesis advances the diagnosis and epidemiology of GCA, most notably in the area of clinical prediction models that aid in the triage of patients with suspected GCA

Self-consistent triaxial de Zeeuw-Carollo Models

We use the usual method of Schwarzschild to construct self-consistent solutions for the triaxial de Zeeuw & Carollo (1996) models with central density cusps. ZC96 models are triaxial generalisations of spherical $\gamma$-models of Dehnen whose densities vary as $r^{-\gamma}$ near the center and $r^{-4}$ at large radii and hence, possess a central density core for $\gamma=0$ and cusps for $\gamma > 0$. We consider four triaxial models from ZC96, two prolate triaxials: $(p, q) = (0.65, 0.60)$ with $\gamma = 1.0$ and 1.5, and two oblate triaxials: $(p, q) = (0.95, 0.60)$ with $\gamma = 1.0$ and 1.5. We compute 4500 orbits in each model for time periods of $10^{5} T_{D}$. We find that a large fraction of the orbits in each model are stochastic by means of their nonzero Liapunov exponents. The stochastic orbits in each model can sustain regular shapes for $\sim 10^{3} T_{D}$ or longer, which suggests that they diffuse slowly through their allowed phase-space. Except for the oblate triaxial models with $\gamma =1.0$, our attempts to construct self-consistent solutions employing only the regular orbits fail for the remaining three models. However, the self-consistent solutions are found to exist for all models when the stochastic and regular orbits are treated in the same way because the mixing-time, $\sim10^{4} T_{D}$, is shorter than the integration time, $10^{5} T_{D}$. Moreover, the ``fully-mixed'' solutions can also be constructed for all models when the stochastic orbits are fully mixed at 15 lowest energy shells. Thus, we conclude that the self-consistent solutions exist for our selected prolate and oblate triaxial models with $\gamma = 1.0$ and 1.5.Comment: 6 Pages, 3 Figures, 2 Tables. Accepted for Publication in A&

Superheated drop as a neutron spectrometer

Superheated drops are known to vaporise when exposed to energetic nuclear radiation since the discovery of bubble chamber. As the degree of superheat increases in a given liquid, less and less energetic neutrons are required to cause nucleation. This property of superheated liquids are being utilised to develope the neutron spectromer. A new principle of neutron spectrometry using Superheated liquid are developed and the developed principle has been tested by Am-Be neutron source.Comment: 9 pages, 8 figures. accepted in Nucl.Instru.MethA,200

Photon sensitivity of superheated drop at room temperature

It has been reported so far that superheated drop detector made of R-12 at room temperature are sensitive to neutrons yet insensitive to photons. This property makes its use as one of the most useful neutron dosimeter. The photon sensitivity of R12 at room temperature when exposed to 59.54kev photons obtained from radioactive Am has been noted for the first time in our laboratory. This discovery is important nt only from the point of view of basic science but more important to the users of R12 in neutron dosimetry to take note of this in assessing the neutron dose correctly.Comment: 3pages, 1 fig. Nuclear Instruments and Method A, 2000, (accepted

On the Mass-Period Distributions and Correlations of Extrasolar Planets

In addition to fitting the data of 233 extra-solar planets with power laws, we construct a correlated mass-period distribution function of extrasolar planets, as the first time in this field. The algorithm to generate a pair of positively correlated beta-distributed random variables is introduced and used for the construction of correlated distribution functions. We investigate the mass-period correlations of extrasolar planets both in the linear and logarithm spaces, determine the confidence intervals of the correlation coefficients, and confirm that there is a positive mass-period correlation for the extrasolar planets. In addition to the paucity of massive close-in planets, which makes the main contribution on this correlation, there are other fine structures for the data in the mass-period plane.Comment: to be published in AJ, tentatively in December 200

Mejora de la logística de abastecimiento y análisis del rol de compras en una empresa de servicios

El proyecto desarrollado tiene como objetivo desarrollar una fuente estratégica para el abastecimiento de empaques a través de la diversificación de proveedores según su capacidad de producción y precio, para disminuir nuestros costos, mejorar la productividad en las máquinas y ser más competitivos. El valor de compra al año del insumo empaques es de $ 3 MM y el 70% del abastecimiento está concentrado en un proveedor lo que ocasiona venta perdida porque no se completa la producción y paros de línea debido a la falta de empaque, adicional se presentan retrasos en el tiempo de entrega del proveedor por tener trabajo en cola y finalmente, los altos costos en el producto final. Las principales causas del problema son reducción de inventarios, aumento de compra de materia prima debido a la adquisición de nueva maquinaria y concentración de compra de empaque en un solo proveedor, es por esto que la empresa debe buscar una fuente estratégica en el insumo de empaques, mediante la diversificación de proveedores según su capacidad de producción y precio ofertado. La metodología de estudio se resume en el planteamiento del problema de investigación, descripción de la situación actual, identificación del problema en valores de costos, análisis del mercado de proveedores, diversificación del volumen, análisis de costos y beneficios de la estrategia. Finalmente se identifican estrategias a corto, mediano y largo plazo que permiten encontrar oportunidades de negocio para la misma empresa, logrando una integración vertical que afianza el crecimiento de la compañía convirtiéndola en una de las principales empresas de toda la corporación

Bloch-Redfield equations for modeling light-harvesting complexes

We challenge the misconception that Bloch-Redfield equations are a less powerful tool than phenomenological Lindblad equations for modeling exciton transport in photosynthetic complexes. This view predominantly originates from an indiscriminate use of the secular approximation. We provide a detailed description of how to model both coherent oscillations and several types of noise, giving explicit examples. All issues with non-positivity are overcome by a consistent straightforward physical noise model. Herein also lies the strength of the Bloch-Redfield approach because it facilitates the analysis of noise-effects by linking them back to physical parameters of the noise environment. This includes temporal and spatial correlations and the strength and type of interaction between the noise and the system of interest. Finally we analyze a prototypical dimer system as well as a 7-site Fenna-Matthews-Olson (FMO) complex in regards to spatial correlation length of the noise, noise strength, temperature and their connection to the transfer time and transfer

Economic differences between cumulative and episodic reduction of sediment from cropland

This study compares measures for reducing cumulative sediment loads from cropland with measures for reducing sediment loads from extreme storms. The issue is whether the optimal means of controlling cumulative loads are very different from the optimal controls for storm event loads. Differences are described in terms of costs and management practices. The analysis entailed developing a storm-event simulation model analogous to the SEDEC sedimentation economics model. The analogue model was used to identify the respective optimal cropland management strategies for various extreme storm conditions. These strategies were then analyzed using the annual average SEDEC, and the optimal strategies from SEDEC were analyzed for their storm-event properties. The comparisons permit conclusions concerning the relative effectiveness of management strategies for achieving cumulative sediment goals versus storm-event load goals. Data for a 223 study site in the Highland-Silver Lake Watershed in Southwestern Illinois were analyzed using this approach. The study produced four main conclusions. First, control costs for episodic sediment loads were consistently higher than the costs for proportionate reductions in annual average loads. Furthermore, strategies for reducing cumulative loads generally achieve less than proportionate reductions in cumulative loads. Second, the highest control costs were generally for the most extreme storms. Third, contour cultivation is a key element of efficient management strategies for row crops. Finally, where a permanent grass crop is grown adjacent to the stream, there is generally little more to be gained by changing upslope management practices. This suggests that grass strips along streams would greatly reduce the need to modify farming practices elsewhere in order to limit sedimentation.U.S. Department of the InteriorU.S. Geological SurveyOpe

Regional Integration of Equity Markets in Sub-Saharan Africa

Equity markets in developing and emerging economies have grown in number and importance as a result of financial market globalisation. However, their role in economic growth and development is enhanced if nascent markets are integrated with well-established ones. Market integration, measured by the transmission of returns volatility, is identified across a sample of SSA countries, using a unique dataset. Evidence for potential integration between financial markets in Sub-Saharan Africa (SSA) is found. Spillovers are found across markets, some unidirectional and others bi-directional. However, continued illiquidity and incomplete institutions indicate that an integrated financial community remains premature, and considerable regulatory reform and harmonisation will be necessary for this to succeed