The application of pulse excitation to ground and flight vibration tests

A discussion of the relative merits of sinusoidal versus nonharmonic excitation for flight flutter testing is presented. It is concluded that the use of transient excitation is rapidly becoming a necessity. The application of small-scale rocket motors to the excitation of the aircraft is suggested. The design and development of rocket motors specifically for flight flutter testing is described. Methods of measuring and analyzing the transient response of the aircraft are discussed, and the techniques of theoretically predicting the structural response are described

Classification of Material Mixtures in Volume Data for Visualization and Modeling

Material classification is a key stop in creating computer graphics models and images from volume data, We present a new algorithm for identifying the distribution of different material types in volumetric datasets such as those produced with Magnetic Resonance Imaging (NMI) or Computed Tomography (CT). The algorithm assumes that voxels can contain more than one material, e.g. both muscle and fat; we wish to compute the relative proportion of each material in the voxels. Other classification methods have utilized Gaussian probability density functions to model the distribution of values within a dataset. These Gaussian basis functions work well for voxels with unmixed materials, but do not work well where the materials are mixed together. We extend this approach by deriving non-Gaussian "mixture" basis functions. We treat a voxel as a volume, not as a single point. We use the distribution of values within each voxel-sized volume to identify materials within the voxel using a probabilistic approach. The technique reduces the classification artifacts that occur along boundaries between materials. The technique is useful for making higher quality geometric models and renderings from volume data, and has the potential to make more accurate volume measurements. It also classifies noisy, low-resolution data well

Partial-volume Bayesian classification of material mixtures in MR volume data using voxel histograms

The authors present a new algorithm for identifying the distribution of different material types in volumetric datasets such as those produced with magnetic resonance imaging (MRI) or computed tomography (CT). Because the authors allow for mixtures of materials and treat voxels as regions, their technique reduces errors that other classification techniques can create along boundaries between materials and is particularly useful for creating accurate geometric models and renderings from volume data. It also has the potential to make volume measurements more accurately and classifies noisy, low-resolution data well. There are two unusual aspects to the authors' approach. First, they assume that, due to partial-volume effects, or blurring, voxels can contain more than one material, e.g., both muscle and fat; the authors compute the relative proportion of each material in the voxels. Second, they incorporate information from neighboring voxels into the classification process by reconstructing a continuous function, ρ(x), from the samples and then looking at the distribution of values that ρ(x) takes on within the region of a voxel. This distribution of values is represented by a histogram taken over the region of the voxel; the mixture of materials that those values measure is identified within the voxel using a probabilistic Bayesian approach that matches the histogram by finding the mixture of materials within each voxel most likely to have created the histogram. The size of regions that the authors classify is chosen to match the sparing of the samples because the spacing is intrinsically related to the minimum feature size that the reconstructed continuous function can represent

Pure phase-encoded MRI and classification of solids

Here, the authors combine a pure phase-encoded magnetic resonance imaging (MRI) method with a new tissue-classification technique to make geometric models of a human tooth. They demonstrate the feasibility of three-dimensional imaging of solids using a conventional 11.7-T NMR spectrometer. In solid-state imaging, confounding line-broadening effects are typically eliminated using coherent averaging methods. Instead, the authors circumvent them by detecting the proton signal at a fixed phase-encode time following the radio-frequency excitation. By a judicious choice of the phase-encode time in the MRI protocol, the authors differentiate enamel and dentine sufficiently to successfully apply a new classification algorithm. This tissue-classification algorithm identifies the distribution of different material types, such as enamel and dentine, in volumetric data. In this algorithm, the authors treat a voxel as a volume, not as a single point, and assume that each voxel may contain more than one material. They use the distribution of MR image intensities within each voxel-sized volume to estimate the relative proportion of each material using a probabilistic approach. This combined approach, involving MRI and data classification, is directly applicable to bone imaging and hard-tissue contrast-based modeling of biological solids

De-aliasing Undersampled Volume Images for Visualization

We present and illustrate a new technique, Image Correlation Supersampling (ICS), for resampling volume data that are undersampled in one dimension. The resulting data satisfies the sampling theorem, and, therefore, many visualization algorithms that assume the theorem is satisfied can be applied to the data. Without the supersampling the visualization algorithms create artifacts due to aliasing. The assumptions made in developing the algorithm are often satisfied by data that is undersampled temporally. Through this supersampling we can completely characterize phenomena with measurements at a coarser temporal sampling rate than would otherwise be necessary. This can save acquisition time and storage space, permit the study of faster phenomena, and allow their study without introducing aliasing artifacts. The resampling technique relies on a priori knowledge of the measured phenomenon, and applies, in particular, to scalar concentration measurements of fluid flow. Because of the characteristics of fluid flow, an image deformation that takes each slice image to the next can be used to calculate intermediate slice images at arbitrarily fine spacing. We determine the deformation with an automatic, multi-resolution algorithm

Erratum for “Effects of a Breast-Health Herbal Formula Supplement on Estrogen Metabolism in Pre- and Post-Menopausal Women not Taking Hormonal Contraceptives or Supplements: A Randomized Controlled Trial”

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Higher order topological actions

In classical mechanics, an action is defined only modulo additive terms which do not modify the equations of motion; in certain cases, these terms are topological quantities. We construct an infinite sequence of higher order topological actions and argue that they play a role in quantum mechanics, and hence can be accessed experimentally.Comment: 7 page

Effects of A Breast-Health Herbal Formula Supplement on Estrogen Metabolism in Pre- and Post-Menopausal Women not Taking Hormonal Contraceptives or Supplements: A Randomized Controlled Trial

Introduction Both indole-3-carbinol and dietary lignans have beneficial effects on estrogen metabolism and breast cancer risk. There is no published literature on the effects of a combination product. This study was designed to investigate the impact of a combination product on estrogen metabolism. The major trial objective was to determine whether a breast health supplement containing indole-3-carbinol and hydroxymatairesinol lignan would alter estrogen metabolism to favour C-2 hydroxylation and reduce C-16 hydroxylation. Higher concentrations of C-2 metabolites and lower concentrations of C-16 metabolites may reduce breast cancer risk and risk for other hormonally-related cancers. Methods Forty-seven pre-menopausal and forty-nine post-menopausal women were recruited for this study, and were divided by random allocation into treatment and placebo group. The treatment supplement contained HMR lignan, indole-3-carbinol, calcium glucarate, milk thistle, Schisandra chinesis and stinging nettle, and each woman consumed either treatment or placebo for 28 days. At day 0 and day 28, blood samples were analysed for serum enterolactone concentrations, and first morning random urine samples were assessed for estrogen metabolites. Repeated measures ANOVA statistical testing was performed. Results In pre-menopausal women, treatment supplementation resulted in a significant increase ( P < 0.05) in urinary 2-OHE concentrations and in the 2:16α-OHE ratio. In post-menopausal women, treatment supplementation resulted in a significant increase in urinary 2-OHE concentrations. In pre- and post-menopausal women combined, treatment supplementation produced a significant increase in urinary 2-OHE concentration and a trend ( P = 0.074) toward an increased 2:16α-OHE ratio. There were no significant increases in serum enterolactone concentrations in the treatment or placebo groups. Conclusions Supplementation with a mixture of indole-3-carbinol and HMR lignan in women significantly increased estrogen C-2 hydroxylation. This may constitute a mechanism for the reduction of breast cancer risk as well as risk for other estrogen-related cancers. Further studies with higher numbers of subjects are indicated. Trial Registration ClinicalTrials.gov registration #NCT01089049

Keeping Unwanted Gulls Away - A Progress Report

Nearly 50 years ago, wires were strung over fish ponds to discourage fish-eating birds from taking fish destined for other uses (McAtee and Piper 1936). Twenty years ago, overwiring of open ditches began on airports to keep ducks from using them and causing hazards to aircraft (Solman 1973). Both techniques used coarse wires spaced closely enough to form a physical barrier to prevent ducks and herons from landing on or taking off from the water

On a Modification of the Boundary State Formalism in Off-shell String Theory

We examine the application of boundary states in computing amplitudes in off-shell open string theory. We find a straightforward generalization of boundary state which produces the correct matrix elements with on-shell closed string states.Comment: Latex, 10 pages, refs added, minor typos correcte