Quadratic irrational integers with partly prescribed continued fraction expansion

We generalise remarks of Euler and of Perron by explaining how to detail all quadratic irrational integers for which the symmetric part of the period of their continued fraction expansion commences with prescribed partial quotients. The function field case is particularly striking.Comment: 10 pages; dedicated to the memory of Bela Brindz

Understanding and recognition of the right ventricular function and dysfunction via a numerical study

The role played by the right ventricular (RV) dysfunction has long been underestimated in clinical practice. Recent findings are progressively confirming that when the RV efficiency deteriorates both the right and the left circulation is (significantly) affected, but studies dedicated to a detailed description of RV hemodynamic role still lack. In response to such a gap in knowledge, this work proposes a numerical model that for the first time evaluates the effect of isolated RV dysfunction on the whole circulation. Lumped parameter modelling was applied to represent the physio-pathological hemodynamics. Different grades of impairment were simulated for three dysfunctions i.e., systolic, diastolic, and combined systolic and diastolic. Hemodynamic alterations (i.e., of blood pressure, flow, global hemodynamic parameters), arising from the dysfunctions, are calculated and analysed. Results well accord with clinical observations, showing that RV dysfunction significantly affects both the pulmonary and systemic hemodynamics. Successful verification against in vivo data proved the clinical potentiality of the model i.e., the capability of identifying the degree of RV impairment for given hemodynamic conditions. This study aims at contributing to the improvement of RV dysfunction recognition and treatment, and to the development of tools for the clinical management of pathologies involving the right heart

Construct Linear Quasi-Interpolants on Infinite Intervals

In solving the data interpolation problem, which is fundamental in data analysis, we typically deal with the data samples spread in a finite interval [a, b], which results in the operations involving finite-dimensional matrices. There are many interesting results developed under this framework. However, when the data samples are given from an infinite interval [a, ∞) (for certain special types of real-world applications), many existing results would not work anymore due to the special properties of the infinite data samples. A new framework should be established to support the infinite data samples. In this dissertation, we develop a special tool called local linear quasi-interpolant for an infinite interval with the following properties: 1) Each linear functional of the quasi-interpolant is determined by at most three data samples, so that the spline coefficients can be calculated in real-time; 2) The quasi-interpolant preserves all the linear polynomials; 3) Our framework does not impose any restriction on the relationship between the sample locations and the spline knots, which provides us the necessary flexibility in the real-world applications. Our construction is based on a matrix factorization method with respect to infinite-dimensional matrices. In order to ensure that the infinite version of the Shoenberg-Whitney matrices are invertible, we take the constructive approach that results in both the left-inverses and the right-inverses. Furthermore, since the associative law of the matrix multiplication does not work for the infinite matrices, we verify all the formulas derived from the infinite matrix operations. Finally, our local method allows us to calculate the spline interpolating coefficients in real-time on the fly for the infinite data samples

Hideous Progeny, Dreaming Robots, and the Limits of the Human

This project is an in-depth exploration and synthesis of three different works: novels Frankenstein by Mary Shelley and Do Androids Dream of Electric Sheep by Philip K. Dick, and the movie Bladerunner by Ridley Scott. I will be approaching each story as a separate entity unto themselves yet tie them together through the common lens of a need to explore what it means to be human, the treatment of those that fall outside of the norm, and how that leads to villainous representation. While the negative portrayal of disabled bodies has positively progressed since Frankenstein, this problem continues to endure within both art and society. Art is merely one facet of a larger problem but by close reading novels and film I hope to gain a better understanding at the the ways in which the disabled body is vilified as well as what it will take to move beyond and into a place of acceptance. By applying theoretical perspectives from aesthetic theory, posthumanism, and disability studies, I argue how evolving perceptions of the body impact our definitions of the villainous

Automatic Image Segmentation of Healthy and Atelectatic Lungs in Computed Tomography

Computed tomography (CT) has become a standard in pulmonary imaging which allows the analysis of diseases like lung nodules, emphysema and embolism. The improved spatial and temporal resolution involves a dramatic increase in the amount of data that has to be stored and processed. This has motivated the development of computer aided diagnostics (CAD) systems that have released the physician from the tedious task of manually delineating the boundary of the structures of interest from such a large number of images, a pre-processing step known as image segmentation. Apart from being impractical, the manual segmentation is prone to high intra and inter observer subjectiveness. Automatic segmentation of the lungs with atelectasis poses a challenge because in CT images they have similar texture and gray level as the surrounding tissue. Consequently, the available graphical information is not sufficient to distinguish the boundary of the lung. The present work aims to close the existing gap left by the segmentation of atelectatic lungs in volume CT data. A-priori knowledge of anatomical information plays a key role in the achievement of this goal

Characterization, prevalence, and risk factors of spontaneous and experimental atherosclerosis and vascular imaging in psittaciformes

Atherosclerosis is a degenerative and inflammatory vascular disease characterized by the accumulation of inflammatory cells, lipids, calcium, and formation of large fibrofatty lesions within the intima of arteries resulting in the disorganization of the arterial wall and stenosis of the lumen. Despite the importance of atherosclerosis in psittacine cardiology, there are few pathologic, clinical, and experimental investigations in psittaciformes. In order to expand the knowledge on psittacine atherosclerosis and provide fundamental observational information for future research, a series of studies was conducted on psittaciformes: 1) psittacine atherosclerotic lesions were characterized and categorized based on histopathology, histochemistry, transmission (TEM), and scanning electron microscopy (SEM) of 63 arterial samples, 2) the prevalence of clinically significant atherosclerotic lesions and the influence of several epidemiological variables were investigated in a multi-center case-control study on 7683 psittaciformes, 3) a diet-induced experimental model of atherosclerosis was developed and characterized in Quaker parrots (Myiopsitta monachus), and 4) a computed-tomography angiographic (CTA) protocol was developed and standardized to image the arterial lumen in Hispaniolan Amazon parrots (Amazona ventralis). Seven lesion types could be described in psittaciformes, which were similar to the human classification system. Digital image analysis, TEM, and SEM helped to further describe the lesions and refine the classification system. Atherosclerosis prevalence significantly increased with age, female sex, and the genera Psittacus, Amazona, and Nymphicus. Mild associations with reproductive, hepatic diseases, and myocardial fibrosis were also evidenced. Experimental induction of atherosclerosis with dietary 1% cholesterol lead to significant lesions within 2 months in Quaker parrots. An increase in arterial and plasma cholesterol and LDL was also documented. Reference limits for arterial luminal diameter of Hispaniolan Amazon parrots were determined by CTA and measurements revealed high intraobserver and interobserver agreement. In conclusion, psittacine atherosclerotic lesions displayed distinctive features that allowed the development of an effective classification system. The prevalence of advanced lesions (type IV-VI) was associated with several risk factors: age, female sex, and three psittacine genera. The Quaker parrot was found to be a suitable experimental model for psittacine atherosclerosis and dyslipidemia. Finally CTA was determined to be safe, reliable, and of potential diagnostic value in parrots for diagnosing stenotic atherosclerotic lesions

Retinal characteristics of myopic eyes in a semi-rural UK population

All levels of myopia are associated with an increased risk of ocular diseases such as glaucoma, and retinal detachment. The prevalence of myopia is increasing at an alarming rate across the globe so an increase in ocular morbidity would be expected unless action is taken. The studies in this thesis were carried out to investigate how the retina, and optic nerve head change in appearance at different levels of myopia. Identification of signs indicating future progression would allow targeting of interventions to minimise the ultimate degree of myopia. This thesis describes four community-based studies investigating retinal appearance in myopic eyes. A mixture of retrospective cross-sectional and longitudinal assessments using previously obtained digital fundus images are presented, along with a prospective cross-sectional study of the peripheral retina. The participants had myopia ≤-0.50 D and were mainly of white European ethnicity. Crescent width was found to increase with both age and level of myopia. Those with inferior-temporally located crescents had the highest levels of myopia. Tilted discs were associated with higher levels of myopia and smaller optic discs. Upon longitudinal assessment of disc measures, the optic cup measures, and crescent width were found to increase. Peripheral retinal lesions were observed in 27 % of eyes. Pigmentary degeneration was the most frequently observed and was associated with increasing age and the widest crescents. White without pressure was found in 5.8 % of eyes and was associated with a higher magnitude of myopia. Static retinal vessel analysis showed no significant relationships between retinal vessel calibre summary measures and myopia, age, or optic nerve head measures. The position of the myopic crescent is a possible predictor of future myopic progression. Further longitudinal study is needed to investigate this. The vertical disc diameter remained constant justifying the use of the quotient of the maximum crescent width to vertical disc diameter to determine crescent width change without the need for magnification correction

Assessment of ocular aberrations at scaled pupil size and reduced Shack-Hartmann spot number

Wavefront aberrations describe the optical imperfections of the eye by measuring the complete refractive elements of the eye. However, the reliability of ocular aberration is uncertain under some challenges and issues. Ocular aberration is generally described in terms of Zernike polynomials. However, the Zernike polynomials are pupil size dependent, therefore, the aberration measured at a fixed pupil size cannot be used for another pupil size. One solution to this problem is to use pupil size scaling technique to scale up or down the aberration to a required pupil size; however, the validity of these techniques for clinical data is not available. To tackle this issue, validation of mathematical pupil size scaling formula by comparing the estimates of the Zernike coefficients with corresponding clinical measurements obtained at different pupil sizes is performed. The results show that the estimation of ocular wavefront aberration coefficients either scaling down from large to smaller pupils or scaling up from smaller to large pupils provides estimates that are not significantly different from clinically measured values. However, when scaling up to a larger pupil size, the estimates are more variable. These findings have implications for pupil scaling on an individual basis, such as in cases of refractive surgery or when using pupil scaling to examine a clinical cohort. Another challenge of an ocular aberration for clinical uses is when the spots on the Shack-Hartmann (SH) are missed due to the opacity of eye parameters or some other disease conditions. This issue is addressed by randomly deleting the number of spots from the SH images and comparing the results with the aberration of the original SH image without the missing spots. The results indicate that as high as 50 % of the SH spots can be deleted without affecting the estimation of spherical defocus within typical clinically acceptable limits of ±0.25D. The results are further examined with in vivo measurements of a human eye wearing a spectacle lens with various models of clustered missing spots to simulate loss that might occur with the disease. The findings of this study provide foundational data on measuring the ocular wavefront aberration when only a reduced number of SH spots are available

Enhancing computer-human interaction with animated facial expressions

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1991.Includes bibliographical references (leaves 87-93).by Brent Cabot James Britton.M.S

An algebraic approach to the quantization of cosntrained systems: finite dimensional examples

From the point of view of canonical quantum gravity, it has become imperative to find a framework for quantization which provides a {\em general} prescription to find the physical inner product, and is flexible enough to accommodate non-canonical variables. In this dissertation I consider an algebraic formulation of the Dirac approach to the quantization of constrained systems, due to A. Ashtekar. The Dirac quantization program is augmented by a general principle to find the inner product on physical states. Essentially, the Hermiticity conditions on physical operators determine this inner product. I also clarify the role in quantum theory of possible algebraic identities between the elementary variables. I use this approach to quantize various finite dimensional systems. Some of these models test the new aspects of the algebraic framework. Others bear qualitative similarities to \gr, and may give some insight into the pitfalls lurking in \qg. In (spatially compact) general relativity, the Hamiltonian is constrained to vanish. I present various approaches one can take to obtain an interpretation of the quantum theory of such ``dynamically constrained'' systems. I apply some of these ideas to the Bianchi I cosmology, and analyze the issue of the initial singularity in quantum theory.Comment: 124 pages, LaTeX (run twice before printing), SU-GP-92/8-1. (Minor corruption (extra blank line at line 2994) hopefully fixed.