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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

Regulation of cardiac responses to increased load:role of endothelin-1, angiotensin II and collagen XV

Piuhola, J. (Jarkko) 14 July 2002 (has links)
Abstract Chronic overload of the heart is the major cause of left ventricular hypertrophy (LVH) and eventually heart failure. It is generally accepted that autocrine/paracrine factors, such as angiotensin II (Ang II) and endothelin-1 (ET-1) contribute to the development of LVH. Cardiac hypertrophy and failure are characterized by attenuated responsiveness to β- adrenergic stimulation and accumulation of collagenous material to the left ventricular wall. The present study aimed to characterize the roles of ET-1 and Ang II in the regulation of cardiac function. The role of the plasmamembrane Ca2+-ATPase (PMCA) in ET-1 induced cardiac responses and the role of type XV collagen in cardiac function were also studied. Both ET-1 infusion and mechanical loading were able to induce positive inotropic effect and induction of early response genes in isolated perfused hearts. ET-1 also induced strong vasoconstriction. Cardiomyocyte-specific PMCA overexpression inhibited the ET-1 induced hypertrophic response, while inotropic response remained unaltered. ET-1 was found to induce release of adrenomedullin (AM), a potent vasorelaxing and inotropic peptide. Infusion of AM antagonized the vasoconstrictive effect of ET-1 independently of nitric oxide. In hypertrophied rat hearts ET-1 was found to contribute significantly to the Frank-Starling response, a fundamental mechanism regulating contractile performance of the heart. In mice hearts, ET-1 was found to play a dual role in load induced elevation of contractile strength: ETA receptors mediated an increase, while ETB receptors mediated an inhibitory effect on contrcatile force. Ang II was not contributing to the contractile response to load in either rat or mice hearts. Blunted response to β-adrenergic stimulus and increased vulnerability as a result of exercise was observed in mice lacking collagen XV. In conclusion, the present results underscore the importance of the local factors, especially ET-1, in regulation of cardiac function, not only in terms of hypertrophic but also in terms of contractile response to load. The results also suggest a role for PMCA in regulation of cardiac function. Lack of type XV collagen was found to result in cardiac dysfunction with many features similar to those of early heart failure.
22

Role of the MoFe Protein β-95-Cysteinyl Residue in Nitrogenase Catalysis in <i>Azotobacter vinelandii</i>

Xie, Haibing 26 August 1998 (has links)
Previous studies revealed that β-95-Cys provides an essential ligand to one of the Fe atoms on the P cluster within the MoFe protein of nitrogenase, and a limited number of substitutions at this position resulted in inactive nitrogenase. It was also found that the counterpart of β-95-Cys, α-88-Cys, which also acts as a cysteinyl ligand to the P cluster, is replaceable without a complete loss of activity. In order to study the structure-function relationship of the protein environment in this region with respect to the P-cluster, subtle changes were introduced at β-95-Cys in <i>Azotobacter vinelandii</I>nitrogenase through site-directed mutagenesis and gene replacement method. Some crude extracts from the mutants with substitutions at β-Cys contain typical FeMo cofactor EPR signal. The β-95<sup>Asp</sup> MoFe protein also has significant nitrogenase activity, but lower, suggesting that β-Cys is not absolutely required for both FeMo cofactor insertion and nitrogenase activity. In order to characterize its catalytic features, the β-95<sup>Asp</sup> MoFe protein was purified from mutant strain DJ1096. It has significantly reduced H⁺ reduction, C₂H₂-reduction and N₂-reduction activity. It was found that a higher percentage of electron flux goes to H⁺ compared to the wild type MoFe protein. It was also found that reductant independent ATP hydrolysis occurs during H⁺ reduction, suggesting that the altered MoFe protein has an increased affinity for Fe protein-ADP complex. Surprisingly, CO has a significant enhancement effect on H⁺ reduction at low electron flux, but not at high electron flux, and highly couples the electron transfer to ATP hydrolysis. These results indicate that the binding of CO to the MoFe protein may either decrease the affinity of Fe-ADP complex for the β-95<sup>Asp</sup> MoFe protein or facilitate electron acceptance by the P cluster, thus improving the electron transfer to substrate. / Master of Science
23

Robust Adaptive Control Design for Classes of SISO and MIMO Linear Systems Under Noisy Output Measurements

Zeng, Sheng 04 April 2007 (has links)
No description available.
24

A Novel Approach for Automatic Quantitation of <sup>31</sup>P Magnetic Resonance Spectroscopy Data

Wang, Xin 20 April 2009 (has links)
No description available.
25

Roles of PMCA Isoforms in Ca<sup>2+</sup>-Homeostasis and Contractility of Bladder Smooth Muscle: Evidence from PMCA Gene-Ablated Mice

Liu, Li 27 June 2007 (has links)
No description available.
26

Decomposição sequencial a partir da sup-representação de W-operadores / Sequential decomposition from Sup-Representation of W-operators

Sanchez Castro, Joel Edu 15 March 2013 (has links)
Os W-operadores são operadores invariantes por translação e localmente definidos dentro de uma janela W. Devido a sua grande utilidade em análise de imagens, estes operadores foram extensamente pesquisados, sendo que uma abordagem para o seu estudo é a partir da Morfologia Matemática. Uma propriedade interessante de W-operadores é que eles possuem uma sup-decomposição, ou seja, um W-operador pode ser decomposto em termos de uma família de operadores sup-geradores que, por sua vez, são parametrizados por elementos da base desse $W$-operador. No entanto, a sup-decomposição tem uma estrutura intrinsecamente paralela que não permite uma implementação eficiente em máquinas de processamento sequencial. Em um trabalho publicado em 2001, Hashimoto e Barrera formalizaram o problema de transformar a sup-decomposição em decomposições puramente sequenciais como um problema de encontrar soluções discretas de uma equação. Neste texto, estendemos o trabalho desenvolvido por eles. Estudamos e exploramos as propriedades matemáticas do problema, e desenvolvemos estratégias heurísticas para encontrar uma decomposição sequencial de um $W$-operador a partir de sua base que seja eficiente ao ser executado. / W-operators are defined as operators which are translation invariant and locally defined within a finite window W. Due to their great contribution to image processing, these operators have been widely researched and used, specially in Mathematical Morphology. An interesting property of W-operators is that they have a sup-decomposition in terms of a family of sup-generating operators, that are parameterized by their basis. However, the sup-decomposition has a parallel structure that is not efficient in sequential machines. In a paper published in 2001, Hashimoto and Barrera formalized the problem of transforming sup-decompositions into purely sequential decompositions as a problem of finding discrete solutions of an equation. In this work, we extend Hashimoto and Barrera\'s approach. We study and explore mathematical properties of this problem and we elaborate heuristic strategies to find a sequential decomposition of a $W$-operator from its basis that can be executed efficiently.
27

DAB Transmission System Simulation / Simulering av ett dataöverföringssystem baserat på DAB standarden

Bilbao, Héctor Uhalte January 2004 (has links)
<p>DAB (Digital Audio Broadcasting) is the radio digital system developed as an european standard by the ETSI, EN 300 400, based on the Eureka-147 group works, to improve the performance of the analogue radio systems (AM and FM). The system is based on the OFDM technology which allows DAB to exploit the spectrum frequencies in a better way with a higher quality of sound for mobile receivers specially. The main part of the OFDM system is based on the FFT algorithms to spread the data flow over different orthogonal carriers. The simulation has been developed in Simulink<sup>TM</sup>and Matlab<sup>TM</sup>and the layout designed follows faithfully the standard for the transmission system. The simulation can be reloaded by the user with the information presented in this thesis. Thus, this work can be continued to complete the DAB whole system simulation. The results obtained running this simulation show the main DAB system characteristics.</p>
28

DAB Transmission System Simulation / Simulering av ett dataöverföringssystem baserat på DAB standarden

Bilbao, Héctor Uhalte January 2004 (has links)
DAB (Digital Audio Broadcasting) is the radio digital system developed as an european standard by the ETSI, EN 300 400, based on the Eureka-147 group works, to improve the performance of the analogue radio systems (AM and FM). The system is based on the OFDM technology which allows DAB to exploit the spectrum frequencies in a better way with a higher quality of sound for mobile receivers specially. The main part of the OFDM system is based on the FFT algorithms to spread the data flow over different orthogonal carriers. The simulation has been developed in Simulink&lt;sup&gt;TM&lt;/sup&gt;and Matlab&lt;sup&gt;TM&lt;/sup&gt;and the layout designed follows faithfully the standard for the transmission system. The simulation can be reloaded by the user with the information presented in this thesis. Thus, this work can be continued to complete the DAB whole system simulation. The results obtained running this simulation show the main DAB system characteristics.
29

Prozesse und Regulation der N2O- und N2-Freisetzung aus Waldböden / Processes and Regulation of Nitrous Oxide and Dinitrogen Emission from Forest Ecosystems

Koch, Anne-Sophie 30 October 2000 (has links)
No description available.
30

Characterization of liquid crystals in porous materials by means of NMR of probe atoms and molecules

Tallavaara, P. (Pekka) 15 May 2008 (has links)
Abstract The present thesis describes a method for characterization of liquid crystals in confined spaces by means of NMR of probe atoms and molecules. 129Xe isotope enriched xenon gas and 13C isotope enriched methyl iodide and methane were used as probes. Behavior of solutes and liquid crystals confined to porous materials was investigated using 129Xe and 13C NMR spectroscopy. Uniaxial nematic liquid crystals Phase 4 and ZLI 1115 were used as a medium. Controlled pore glass with well defined and known properties was used as a porous material. The behavior of liquid crystals and solutes in various different size pores, temperatures and magnetic fields at different solute concentrations was explained. The average pore diameter of the material varied from mesopores to macropores. The studied temperature range covered solid, nematic and isotropic phases of bulk liquid crystals, and the highest magnetic field was 2.5 times stronger than the lowest one used (4.70 T). The chemical shifts, intensities, and line shapes of the resonance signals from the solutes were observed to contain lots of information about the effect of confinement on the state of the liquid crystals. Especially the line shape of the 13C resonances of methyl iodide was observed to be very sensitive to the liquid crystal orientation distribution in the pores. By varying experimental conditions the relative contribution of field and the surface forces of pore walls to the orientation of liquid crystal molecules inside the pores was seen to change quite drastically. In addition, it was also observed that when the sample is cooled very rapidly, xenon atoms do not squeeze out from the freezing medium but they are occluded inside the solid lattice, and their chemical shift is very sensitive to crystal structure. Furthermore, because solutes experienced on average isotropic environment inside the smallest pores, isotropic value of the shielding tensor could be determined at exactly the same condition and temperature as anisotropic counterpart between the pore particles. Thus, for the first time in the solution state, shielding anisotropies could be determined as a function of temperature.

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