Three-dimensional reconstruction from projections

summary:Computerized tomograhphy is a technique for computation and visualization of density (i.e. X- or $\gamma$-ray absorption coefficients) distribution over a cross-sectional anatomic plane from a set of projections. Three-dimensional reconstruction may be obtained by using a system of parallel planes. For the reconstruction of the transverse section it is necessary to choose an appropriate method taking into account the geometry of the data collection, the noise in projection data, the amount of data, the computer power available, the accuracy required etc. In the paper the theory related to the convolution reconstruction methods is reviewed. The principal contribution consists in the exact mathematical treatment of Radon's inverse transform based on the concepts of the regularization of a function and the generalized function. This approach naturally leads to the employment of the generalized Fourier transform. Reconstructions using simulated projection data are presented for both the parallel and divergent-ray collection geometries

Inheritance of Black Hair Patterns in Cattle Lacking the Extension Factor for Black (E.). III, A Multiple Allelic Hypothesis to Explain the Inheritance of Blackish and Blackish Pattern

Author Institution: Department of Dairy Science and the Institute of Genetics, The Ohio State University, Columbus and Department of Dairy Science, The Ohio Agricultural Experiment Station, Wooste

High temperature dielectric properties of Apical, Kapton, Peek, Teflon AF, and Upilex polymers

Reliable lightweight systems capable of providing electrical power at the magawatt level are a requirement for future manned space exploration missions. This can be achieved by the development of high temperature insulating materials which are not only capable of surviving the hostile space environment but can contribute to reducing the mass and weight of the heat rejection system. In this work, Apical, Upilex, Kapton, Teflon AF, and Peek polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 C. The materials are also tested in terms of their dielectric constant and dissipation factor at high temperatures with an electrical stress of 60 Hz, 200 V/mil present. The effects of thermal aging on the properties of the films are determined after 15 hours of exposure to 200 and 250 C, each. The results obtained are discussed and conclusions are made concerning the suitability of these dielectrics for use in capacitors and cable insulations in high temperature environments

The Evolution of X-ray Bursts in the "Bursting Pulsar" GRO J1744-28

GRO J1744-28, commonly known as the `Bursting Pulsar', is a low mass X-ray binary containing a neutron star and an evolved giant star. This system, together with the Rapid Burster (MXB 1730-33), are the only two systems that display the so-called Type II X-ray bursts. These type of bursts, which last for 10s of seconds, are thought to be caused by viscous instabilities in the disk; however the Type II bursts seen in GRO J1744-28 are qualitatively very different from those seen in the archetypal Type II bursting source the Rapid Burster. To understand these differences and to create a framework for future study, we perform a study of all X-ray observations of all 3 known outbursts of the Bursting Pulsar which contained Type II bursts, including a population study of all Type II X-ray bursts seen by RXTE. We find that the bursts from this source are best described in four distinct phenomena or `classes' and that the characteristics of the bursts evolve in a predictable way. We compare our results with what is known for the Rapid Burster and put out results in the context of models that try to explain this phenomena.Comment: Accepted to MNRAS Aug 17 201

Displacement sensing using bi-modal resonance in over-coupled inductors

This paper presents the theory and key experimental findings for an investigation into the generation of bimodal resonance (frequency splitting) phenomena in mutually over-coupled inductive sensors, and its exploitation to evaluate relative separation and angular displacement between coils. This innovative measurement technique explores the bimodal resonant phenomena observed between two coil designs - solenoid and planar coil geometries. The proposed sensors are evaluated against first-order analytical functions and finite element models, before experimentally validating the predicted phenomenon for the different sensor configurations. The simulated and experimental results show excellent agreement and first-order best-fit functions are employed to predict displacement variables experimentally. Co-planar separation and angular displacement are shown to be experimentally predictable to within $\pm1mm$ and $\pm1^o$ using this approach. This study validates the first-order physics-based models employed, and demonstrates the first proof-of-principle for using resonant phenomena in inductive array sensors for evaluating relative displacement between array elements

Deterministic epidemic models overestimate the basic reproduction number of observed outbreaks

The basic reproduction number, $R_0$, is a well-known quantifier of epidemic spread. However, a class of existing methods for estimating this quantity from epidemic incidence data can lead to an over-estimation of this quantity. In particular, when fitting deterministic models to estimate the rate of spread, we do not account for the stochastic nature of epidemics and that, given the same system, some outbreaks may lead to epidemics and some may not. Typically, an observed epidemic that we wish to control is a major outbreak. This amounts to implicit selection for major outbreaks which leads to the over-estimation problem. We show that by conditioning a `deterministic' model on major outbreaks, we can more reliably estimate the basic reproduction number from an observed epidemic trajectory

Displacement sensing using bi-modal resonance in over-coupled inductors

This paper presents the theory and key experimental findings for an investigation into the generation of bimodal resonance (frequency splitting) phenomena in mutually over-coupled inductive sensors, and its exploitation to evaluate relative separation and angular displacement between coils. This innovative measurement technique explores the bimodal resonant phenomena observed between two coil designs - solenoid and planar coil geometries. The proposed sensors are evaluated against first-order analytical functions and finite element models, before experimentally validating the predicted phenomenon for the different sensor configurations. The simulated and experimental results show excellent agreement and first-order best-fit functions are employed to predict displacement variables experimentally. Co-planar separation and angular displacement are shown to be experimentally predictable to within $\pm1mm$ and $\pm1^o$ using this approach. This study validates the first-order physics-based models employed, and demonstrates the first proof-of-principle for using resonant phenomena in inductive array sensors for evaluating relative displacement between array elements