801 research outputs found
The effect of sodium tetradecyl sulphate on coagulation and endothelium.
A thesis submitted to the Faculty of Medicine,
University of the Witwatersrand, for the
degree of Doctor of Philosophy in Medicine.Despite having been initially described more than fifty
years ago, sclerotherapy of oesophageal varices has only
relatively recently became regarded as one of the primary
modalities both to control bleeding oesophageal varices and
to prevent recurrent bleeding. Sclerotherapy, however, ts
associated with numerous complications and its exact
mechanism of action, particularly that pertaining to its
effect on haemostasis, has to date been poorly
documented. One of the problems of comparing the various
trials has been the diversity of both the technique and the
type and concentration of the sclerosants used. (Abbreviation abstract)Andrew Chakane 201
Combined-channel instantaneous frequency analysis for audio source separation based on comodulation
Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2008.Includes bibliographical references (p. 295-303).Normal human listeners have a remarkable ability to focus on a single sound or speaker of interest and to block out competing sound sources. Individuals with hearing impairments, on the other hand, often experience great difficulty in noisy environments. The goal of our research is to develop novel signal processing methods inspired by neural auditory processing that can improve current speech separation systems. These could potentially be of use as assistive devices for the hearing impaired, and in many other communications applications. Our focus is the monaural case where spatial information is not available. Much perceptual evidence indicates that detecting common amplitude and frequency variation in acoustic signals plays an important role in the separation process. The physical mechanisms of sound generation in many sources cause common onsets/offsets and correlated increases/decreases in both amplitude and frequency among the spectral components of an individual source, which can potentially serve as a distinct signature. However, harnessing these common modulation patterns is difficult because when spectral components of competing sources overlap within the bandwidth of a single auditory filter, the modulation envelope of the resultant waveform resembles that of neither source. To overcome this, for the coherent, constant-frequency AM case, we derive a set of matrix equations which describes the mixture, and we prove that there exists a unique factorization under certain constraints. These constraints provide insight into the importance of onset cues in source separation. We develop algorithms for solving the system in those cases in which a unique solution exists. This work has direct bearing on the general theory of non-negative matrix factorization which has recently been applied to various problems in biology and learning. For the general, incoherent, AM and FM case, the situation is far more complex because constructive and destructive interference between sources causes amplitude fluctuations within channels that obscures the modulation patterns of individual sources.(cont.) Motivated by the importance of temporal processing in the auditory system, and specifically, the use of extrema, we explore novel methods for estimating instantaneous amplitude, frequency, and phase of mixtures of sinusoids by comparing the location of local maxima of waveforms from various frequency channels. By using an overlapping exponential filter bank model with properties resembling the cochlea, and combining information from multiple frequency bands, we are able to achieve extremely high frequency and time resolution. This allows us to isolate and track the behavior of individual spectral components which can be compared and grouped with others of like type. Our work includes both computational and analytic approaches to the general problem. Two suites of tests were performed. The first were comparative evaluations of three filter-bank-based algorithms on sets of harmonic-like signals with constant frequencies. One of these algorithms was selected for further performance tests on more complex waveforms, including AM and FM signals of various types, harmonic sets in noise, and actual recordings of male and female speakers, both individual and mixed. For the frequency-varying case, initial results of signal analysis with our methods appear to resolve individual sidebands of single harmonics on short time scales, and raise interesting conceptual questions on how to define, use and interpret the concept of instantaneous frequency. Based on our results, we revisit a number of questions in current auditory research, including the need for both rate and place coding, the asymmetrical shapes of auditory filters, and a possible explanation for the deficit of the hearing impaired in noise.by Barry David Jacobson.Ph.D
Delayed hypersensitivity to low molecular weight heparin (LMWH) in pregnancy
Heparin is currently the anticoagulant of choice for the prevention and treatment of thrombo-embolic disease in pregnancy because it does not cross the placenta [1]. The use of low molecular weight heparin (LMWH) is preferred to unfractionated heparin (UFH) as it is associated with a lower risk of bleeding, osteoporosis, heparin induced thrombocytopenia (HIT) and hypersensitivity reactions [2, 3, 4, 5]. Fondaparinux can be considered as a valuable alternative to LMWH during pregnancy in those patients with heparin induced skin reactions and/or HIT
MSEC2006-21131 TOOL RUNOUT ESTIMATION USING FEED FORCE SPECTRAL COMPONENTS
ABSTRACT Cutter Runout is the eccentricity caused by a combination of imperfections in the cutting tool, tool holder, and spindle. While magnitudes of cutter runout are generally small (e.g 10 µm), the effect is noticeable in high tolerance finishing operations, and can cause significant variations in the force experienced on a multi tooth cutter. The goal of this research is to design and evaluate an indirect runout estimation method, using feed force components at the spindle and tooth passing frequency. The accuracy of the method is evaluated for a range of cutting conditions for 4 and 6 tooth helical flat end mills. The standard error of the runout estimation method for 27 test cases was determined to be 7.1 µm. The error was skewed by several data points from a 6 tooth cutter. Additional testing is needed with 2, 3 and 5 tooth cutters. INTRODUCTION The effect of tool runou
Book Reviews
Reviews of the following books: Island in Time: A Natural and Human History of the Islands of Maine by Philip W. Conkling; A Seafaring Legacy: The Photographs, Diaries and Memorabilia of a Maine Sea Captain and His Wife by Julianna FreeHand; Coming of Age on Damariscove Island, Maine by Carl R. Griffin III and Alaric Faulkner; The Identity of the St. Francis Indians by Gordon M. Day; Soldiers, Sailors and Patriots of the Revolutionary War: Maine by Carleton E. Fisher and Sue K. Fisher
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A Variable Polyglutamine Repeat Affects Subcellular Localization and Regulatory Activity of a Populus ANGUSTIFOLIA Protein.
Polyglutamine (polyQ) stretches have been reported to occur in proteins across many organisms including animals, fungi and plants. Expansion of these repeats has attracted much attention due their associations with numerous human diseases including Huntington's and other neurological maladies. This suggests that the relative length of polyQ stretches is an important modulator of their function. Here, we report the identification of a Populus C-terminus binding protein (CtBP) ANGUSTIFOLIA (PtAN1) which contains a polyQ stretch whose functional relevance had not been established. Analysis of 917 resequenced Populus trichocarpa genotypes revealed three allelic variants at this locus encoding 11-, 13- and 15-glutamine residues. Transient expression assays using Populus leaf mesophyll protoplasts revealed that the 11Q variant exhibited strong nuclear localization whereas the 15Q variant was only found in the cytosol, with the 13Q variant exhibiting localization in both subcellular compartments. We assessed functional implications by evaluating expression changes of putative PtAN1 targets in response to overexpression of the three allelic variants and observed allele-specific differences in expression levels of putative targets. Our results provide evidence that variation in polyQ length modulates PtAN1 function by altering subcellular localization
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