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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Three Essays on Spectral Analysis and Dynamic Factors

Liska, Roman 10 September 2008 (has links)
The main objective of this work is to propose new procedures for the general dynamic factor analysis introduced by Forni et al. (2000). First, we develop an identification method for determining the number of common shocks in the general dynamic factor model. Sufficient conditions for consistency of the criterion are provided for large n (number of series) and T (the series length). We believe that our procedure can shed light on the ongoing debate on the number of factors driving the US or Eurozone economy. Second, we show how the dynamic factor analysis method proposed in Forni et al. (2000), combined with our identification method, allows for identifying and estimating joint and block-specific common factors. This leads to a more sophisticated analysis of the structures of dynamic interrelations within and between the blocks in suchdatasets. Besides the framework of the general dynamic factor model we also propose a consistent lag window spectral density estimator based on multivariate M-estimators by Maronna (1976) when the underlying data are coming from the alpha mixing stationary Gaussian process.
22

Role of Glutamatergic Neurotransmission at the Nucleus Reticularis Ventrolateralis during Experimental Endotoxemia

Chang, Pi-Shan 26 June 2001 (has links)
The components of SAP signals of low- frequency (LF: 0.08-0.15 Hz) and very low- frequency (VLF: 0.00-0.08 Hz) related with vasomotor tone that reflects the activity of sympathetic premotor neuron in the nucleus reticularis ventrolateralis (NRVL). The Sprague-Dawely male rats with acute endotoxemia (lipopolysaccharide, LPS; 15 mg/Kg i.v.) induced a reduction phase (phase¢¹), followed by partial recovery (phase¢º) and a secondary decrease (phase ¢»). The rats with acute endotoxemia display three phases based on change in the power density of LF and VLF component. Pretreatment with microinjection of NMDA receptor antagonist, MK-801, and non-NMDA receptor antagonist, CNQX into the bilaterial NRVL prolong the survival time and prolong the duration time of phase¢º and phase¢». Pretreatment with high concentration MK-801 (200 pmol) and CNQX (10 pmol) hold the MSAP and heart rate in the steady state and decrease the slope of MSAP falling during endotoxemia.The power density of pretreatment with high concentration MK-801 (200 pmol) and CNQX (10 pmol) was deceease. We conclude that the rat during experimental endotoxemia decrease the duration time of NMDA and non-NMDA receptor activity in NRVL. The NMDA receptor and non-NMDA receptor activity in NRVL during endotoxemia contribute the slope of MSAP falling and cause to death.
23

Spectral problems of optical waveguides and quantum graphs

Ong, Beng Seong 30 October 2006 (has links)
In this dissertation, we consider some spectral problems of optical waveguide and quantum graph theories. We study spectral problems that arise when considerating optical waveguides in photonic band-gap (PBG) materials. Specifically, we address the issue of the existence of modes guided by linear defects in photonic crystals. Such modes can be created for frequencies in the spectral gaps of the bulk material and thus are evanescent in the bulk (i.e., confined to the guide). In the quantum graph part we prove the validity of the limiting absorption principle for finite graphs with infinite leads attached. In particular, this leads to the absence of a singular continuous spectrum. Another problem in quantum graph theory that we consider involves opening gaps in the spectrum of a quantum graph by replacing each vertex of the original graph with a finite graph. We show that such "decorations" can be used to create spectral gaps.
24

Vanishing properties and spectral analysis in the Kerzman-Stein theory /

January 2001 (has links)
Thesis (Ph. D.)--University of Chicago, Dept. of Mathematics, June 2001. / Includes bibliographical references. Also available on the Internet.
25

Computer-aided studies on luminescence spectroscopy in pharmaceutical analysis

Clark, Brian John January 1985 (has links)
No description available.
26

Spectroscopic studies of coal and an ESR study of mono and dicarbonyl radical cations

Portwood, Lynn January 1987 (has links)
Part I - ESR spectra of pure coals, oils and tars are presented; their g values and linewidths are calculated. Almost all the spectra are single, broad resonances; but one coal, Hucknall Coal, exhibits a two line spectrum, a narrow line superimposed on a broad line. On admission of oxygen the narrow line is reversibly lost. On the addition of various solvents to the samples, in most cases, an irreversible loss in ESR signal intensity was observed. There seems to be no direct correlation between which solvent is added to which coal and the effect on the ESR signal intensity. Infra-red spectra of pure coals are studied, both as pressed discs and thin films, and a method for the preparation of these discs and films is given. Solvent addition experiments were undertaken and the results show the breaking of weak coal/water hydrogen bonds and the formation of stronger coal/solvent hydrogen bonds. Part II - ESR spectra of the radical cations of several mono and dicarbonyl compounds are presented and interpretation of these spectra are given. For most compounds the parent radical cation is seen, with the spin on oxygen. The cyclic dicarbonyls show the σ-bonded structure for the cation with coupling to the protons δ to the spin. Some non-aldehydic dicarbonyls show a rearranged structure with the spin on carbon. The aldehydic dicarbonyls all show, in addition to the parent radical cation, lines due to an acetal type species, as yet unidentified. Some compounds containing nitrogen or sulphur in addition to oxygen have the spin localised onto these alternative heteroatoms.
27

Detection of partial areas using remote sensing and hydrological analyses /

Kolawole, Michael O. January 1988 (has links) (PDF)
Thesis (M. Env. St.)--University of Adelaide, Centre for Environmental Studies, 1989. / Two coloured folded plates in pocket. Includes bibliographical references (leaves 97-107).
28

Radiative combined-mode heat transfer in a multi-dimensional participating medium using spectral methods /

Lan, Chao-ho, January 2000 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 156-164). Available also in a digital version from Dissertation Abstracts.
29

Application of phenology to assist in hyperspectral species classification of a northern hardwood forest /

Sprehe, Gretchen M. January 2005 (has links)
Thesis (M.S.)--Rochester Institute of Technology, 2005. / Typescript. Includes bibliographical references (leaves 93-96).
30

Isospectral orbifold lens spaces

Shams-Ul-Bari, Naveed January 2016 (has links)
Spectral theory is the study of Mark Kac's famous question [K], "can one hear the shape of a drum?" That is, can we determine the geometrical or topological properties of a manifold by using its Laplace Spectrum? In recent years, the problem has been extended to include the study of Riemannian orbifolds within the same context. In this thesis, on the one hand, we answer Kac's question in the negative for orbifolds that are spherical space forms of dimension higher than eight. On the other hand, for the three-dimensional and four-dimensional cases, we answer Kac's question in the affirmative for orbifold lens spaces, which are spherical space forms with cyclic fundamental groups. We also show that the isotropy types and the topology of the singularities of Riemannian orbifolds are not determined by the Laplace spectrum. This is done in a joint work with E. Stanhope and D. Webb by using P. Berard's generalization of T. Sunada's theorem to obtain isospectral orbifolds. Finally, we construct a technique to get examples of orbifold lens spaces that are not isospectral, but have the same asymptotic expansion of the heat kernel. There are several examples of such pairs in the manifold setting, but to the author's knowledge, the examples developed in this thesis are among the first such examples in the orbifold setting.

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