URV ESPRIT for tracking time-varying signals Liu, K.J. Ray; O'Leary, D.P.; Stewart, G.W. ...
IEEE transactions on signal processing,
12/1994, Letnik:
42, Številka:
12
Journal Article
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ESPRIT is an algorithm for determining the fixed directions of arrival of a set of narrowband signals at an array of sensors. Unfortunately, its computational burden makes it unsuitable for real time ...processing of signals with time-varying directions of arrival. The authors develop a new implementation of ESPRIT that has potential for real time processing. It is based on a rank-revealing URV decomposition, rather than the eigendecomposition or singular value decomposition used in previous ESPRIT algorithms. The authors demonstrate its performance on simulated data representing both constant and time-varying signals. They find that the URV-based ESPRIT algorithm is effective for estimating time-varying directions-of-arrival at considerable computational savings over the SVD-based algorithm.< >
SUMMARY
1. The roles of adenosine and adenosine 5′‐triphosphate in cardiorespiratory regulation by the nucleus tractus solitarius (NTS) have been evaluated in a range of experiments, using ...microinjections of selective agonists and antagonists of purinoceptors.
2. Adenosine injected into the caudal NTS decreases heart rate (HR), arterial blood pressure (BP) and respiratory frequency by an action at A2a receptors on glutamatergic nerve terminals. Microinjections of the A2a agonist CGS 21680 caused falls in arterial BPand HR which were selectively antagonized by the A2a antagonist CGS 15943. Injection of the Ai agonist CPA in the caudal NTS elevated BP and HR and its actions were selectively antagonized by the Ai antagonist l,3‐dipropyl‐8‐cyclopentylxan‐thine. Adenosine enhanced glutamate release in the NTS.
3. In the rostral NTS, adenosine administration resulted in an elevation of BP.
4. ATP microinjection into the subpostremal NTS depressed HR and BP by an action on P2x purinoceptors, which are blocked by suramin. ATP microinjections differentially affected vascular conductance in regional peripheral vascular beds, with the most marked increases in conductance in the iliac bed and lesser effects in the superior mesenteric and renal vascular beds.
5. Recordings from renal and lumbar sympathetic nerves have demonstrated marked dose‐dependent decreases in efferent activity following α, β‐methylene ATP injections into the NTS; however, only renal but not lumbar sympathetic nerve activity was inhibited following CGS 21680 injections into the same site of the NTS.
6. ATP may function as a fast‐acting neurotransmitter in the baroreceptor afferent pathway or in interneurons in the NTS. Adenosine is likely to play a role as a modulator of activity in baroreceptor and chemoreceptor pathways, fine tuning the functional output of both systems.
The physical considerations of using dual isotope brain SPECT imaging to monitor blood flow changes during cognitive activation studies were investigated. These factors included field uniformity, ...spatial resolution and crosstalk. Serial dual isotope single photon emission computed tomographic (SPECT) studies of a test tube phantom and an anthropomorphic brain phantom filled with 99Tcm and 123I were made over a 10 h period. The reconstructed counts in the 99Tcm and 123I windows were corrected for crosstalk and were plotted as a function of time. The plotted data from each window decreased over time with a half-life characteristic of each radionuclide. The relative difference between true 123I and 99Tcm region counts has to be of the order of 10% to be statistically significant at the P < 0.05 level.
Attributions of blame for the first and latest episodes of violence were assessed in a sample of 139 couples who were referred to a mandatory domestic violence treatment program in the military. ...Results found that men were significantly more likely to blame themselves for the latest rather than for the first episode.
A dual isotope, single photon emission tomography (SPECT) technique using 99Tcm-hexamethylpropyleneamine oxime (HMPAO) and 123I-iodoamphetamine (IMP) was investigated to determine its suitability for ...assessing regional cerebral blood flow (rCBF) changes resulting from cognitive activation. The similarity of the 123I-IMP and 99Tcm-HMPAO distributions under the same physiological conditions was first investigated by administering the two agents to human subjects (n = 8) either simultaneously or at different times but during the performance of the same task. Normalized ratio images generated from the 99Tcm and 123I data showed that the two tracers distributed similarly in the left and right cerebral hemispheres when administered under similar physiological conditions. There was, however, a significant anterior/posterior gradient that appears to be the result of partial volume effects due to small differences in spatial resolution of the two agents. In two subjects, 99Tcm-HMPAO was administered during a resting period with eyes-closed and 123I-IMP was injected later during visual checkerboard stimulation. Ratio images showed a localized increase in the occipital lobes during the visual stimulation consistent with the expected increase in rCBF. The dual isotope strategy appears promising for study of changes in rCBF due to cognitive activation.
IMPORTANCE: Focal cortical dysplasia (FCD), hemimegalencephaly, and megalencephaly constitute a spectrum of malformations of cortical development with shared neuropathologic features. These disorders ...are associated with significant childhood morbidity and mortality. OBJECTIVE: To identify the underlying molecular cause of FCD, hemimegalencephaly, and diffuse megalencephaly. DESIGN, SETTING, AND PARTICIPANTS: Patients with FCD, hemimegalencephaly, or megalencephaly (mean age, 11.7 years; range, 2-32 years) were recruited from Pediatric Hospital A. Meyer, the University of Hong Kong, and Seattle Children’s Research Institute from June 2012 to June 2014. Whole-exome sequencing (WES) was performed on 8 children with FCD or hemimegalencephaly using standard-depth (50-60X) sequencing in peripheral samples (blood, saliva, or skin) from the affected child and their parents and deep (150-180X) sequencing in affected brain tissue. Targeted sequencing and WES were used to screen 93 children with molecularly unexplained diffuse or focal brain overgrowth. Histopathologic and functional assays of phosphatidylinositol 3-kinase–AKT (serine/threonine kinase)–mammalian target of rapamycin (mTOR) pathway activity in resected brain tissue and cultured neurons were performed to validate mutations. MAIN OUTCOMES AND MEASURES: Whole-exome sequencing and targeted sequencing identified variants associated with this spectrum of developmental brain disorders. RESULTS: Low-level mosaic mutations of MTOR were identified in brain tissue in 4 children with FCD type 2a with alternative allele fractions ranging from 0.012 to 0.086. Intermediate-level mosaic mutation of MTOR (p.Thr1977Ile) was also identified in 3 unrelated children with diffuse megalencephaly and pigmentary mosaicism in skin. Finally, a constitutional de novo mutation of MTOR (p.Glu1799Lys) was identified in 3 unrelated children with diffuse megalencephaly and intellectual disability. Molecular and functional analysis in 2 children with FCD2a from whom multiple affected brain tissue samples were available revealed a mutation gradient with an epicenter in the most epileptogenic area. When expressed in cultured neurons, all MTOR mutations identified here drive constitutive activation of mTOR complex 1 and enlarged neuronal size. CONCLUSIONS AND RELEVANCE: In this study, mutations of MTOR were associated with a spectrum of brain overgrowth phenotypes extending from FCD type 2a to diffuse megalencephaly, distinguished by different mutations and levels of mosaicism. These mutations may be sufficient to cause cellular hypertrophy in cultured neurons and may provide a demonstration of the pattern of mosaicism in brain and substantiate the link between mosaic mutations of MTOR and pigmentary mosaicism in skin.
This essay develops a theory of apocalyptic texts and movements by applying Kenneth Burke's conception of the tragic and comic frames of acceptance to the text of the Christian Apocalypse and to the ...history of its interpretation. Burke's "psychology of form" is used to explain the recurring patterns of apocalyptic argument as functions of rhetor/audience interaction. Viewing the Apocalypse as an epochal rhetoric that structures human experience of temporality through the rhythms of drama leads to insights on the possibilities and limitations of interpretive argument.
The results of recent research indicate that the progeny of proliferating cells in the subventricular zone can differentiate in vitro into neurons and glia after completing their last division in the ...adult brain.
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